ARECIBO, P.R. -- Despite evidence from two space probes in the 1990s, radar astronomers say they can find no signs of thick ice at the moon's poles. If there is water at the lunar poles, the researchers say, it is widely scattered and permanently frozen inside the dust layers, something akin to terrestrial permafrost.
Using the 70-centimeter (cm)-wavelength radar system at the National Science Foundation's (NSF) Arecibo Observatory, Puerto Rico, the research group sent signals deeper into the lunar polar surface -- more than five meters (about 5.5 yards) -- than ever before at this spatial resolution. "If there is ice at the poles, the only way left to test it is to go there directly and melt a small volume around the dust and look for water with a mass spectrometer," says Bruce Campbell of the Center for Earth and Planetary Studies at the Smithsonian Institution.
Campbell is the lead author of an article, "Long-Wavelength Radar Probing of the Lunar Poles," in the Nov. 13, 2003, issue of the journal Nature. His collaborators on the latest radar probe of the moon were Donald Campbell, professor of astronomy at Cornell University; J.F. Chandler of Smithsonian Astrophysical Observatory; and Alice Hine, Mike Nolan and Phil Perillat of the Arecibo Observatory, which is managed by the National Astronomy and Ionosphere Center at Cornell for the NSF.
Suggestions of lunar ice first came in 1996 when radio data from the Clementine spacecraft gave some indications of the presence of ice on the wall of a crater at the moon's south pole. Then, neutron spectrometer data from the Lunar Prospector spacecraft, launched in 1998, indicated the presence of hydrogen, and by inference, water, at a depth of about a meter at the lunar poles. But radar probes by the 12-cm-wavelength radar at Arecibo showed no evidence of thick ice at depths of up to a meter. "Lunar Prospector had found significant concentrations of hydrogen at the lunar poles equivalent to water ice at concentrations of a few percent of the lunar soil," says Donald Campbell. "There have been suggestions that it may be in the form of thick deposits of ice at some depth, but this new data from Arecibo makes that unlikely."
Says Bruce Campbell, "There are no places that we have looked at with any of these wavelengths where you see that kind of signature."
The Nature paper notes that if ice does exist at the lunar poles it would be considerably different from "the thick, coherent layers of ice observed in shadowed craters on Mercury," found in Arecibo radar imaging. "On Mercury what you see are quite thick deposits on the order of a meter or more buried by, at most, a shallow layer of dust. That's the scenario we were trying to nail down for the moon," says Bruce Campbell. The difference between Mercury and the moon, the researchers say, could be due to the lower average rate of comets striking the lunar surface, to recent comet impacts on Mercury or to a more rapid loss of ice on the moon.
What makes the lunar poles good cold traps for water is a temperature of minus 173 degrees Celsius (minus 280 degrees Fahrenheit). The limb of the sun rises only about two degrees above the horizon at the lunar poles so that sunlight never penetrates into deep craters, and a person standing on the crater floor would never see the sun. The Arecibo radar probed the floors of two craters in permanent shadow at the lunar south pole, Shoemaker and Faustini, and, at the north pole, the floors of Hermite and several small craters within the large crater Peary. In contrast, Clementine focused on the sloping walls of Shackleton crater, whose floor can't be "seen" from Earth. "There is a debate on how to interpret data from a rough, tilted surface," says Bruce Campbell.
The Arecibo radar probe is a particularly good detector of thick ice because it takes advantage of a phenomenon known as "coherent backscatter." Radar waves can travel long distances without being absorbed in ice at temperatures well below freezing. Reflections from irregularities inside the ice produce a very strong radar echo. In contrast, lunar soil is much more absorptive and does not give as strong a radar echo.
Related World Wide Web sites: The following sites provide additional information on this news release. Some might not be part of the Cornell University community, and Cornell has no control over their content or availability.
MURRAY HILL, N. J. - Hurtling through the frigid expanse beyond the planets, NASA's aging spacecraft Voyager 1 has reached the edge of the Solar System, where it has encountered a massive shock wave, according to a paper that will be published in Nature on Nov 6, 2003, by a team of scientists that includes Louis Lanzerotti of Bell Labs, the research and development arm of Lucent Technologies.
More than eight billion miles from Earth, the farthest an operating spacecraft has ever journeyed, Voyager 1 is providing scientists with data from a fascinating yet little understood region of space - the frontier where the Sun's influence begins to wane, and the tenuous vastness of interstellar space takes over.
It is here that charged particles streaming out from the Sun - called the solar wind - bump into the ionized gas and dust that is spread thinly between stars, causing a shock wave in the process.
Data of how the solar wind behaves will provide scientists with knowledge useful not only to astronomy but to terrestrial concerns such as how solar emissions affect wireless telephone calls, satellite communications and electric power grids.
"When the Voyager missions were launched in 1977, we never thought the instruments we developed more than three decades ago would one day probe the edge of the Solar System," said Lanzerotti, an expert on how the solar wind affects terrestrial communications. Lanzerotti joined Bell Labs in 1965 and has been involved with NASA's Voyager missions since their inception in 1972. In honor of his contributions to space physics, the International Astronomical Union has named an asteroid after him, Minor Planet 5504 Lanzerotti. He now divides his time between Bell Labs, where he is a consultant, and the New Jersey Institute of Technology, where he is a distinguished professor at the Center for Solar Terrestrial Research.
"Voyager 1 and 2 provided us with unparalleled views of the planets. I find it very exciting that Voyager 1 will soon begin to explore the vastness of the interstellar medium," he said.
Astronomers now know that the space between stars, once thought to be completely empty, is filled with a dilute plasma of gas and dust termed the interstellar medium. The solar wind blows out a giant bubble called the heliosphere within the interstellar medium, and the boundary between the heliosphere and the interstellar medium is a place where a lot of interesting physical phenomena take place.
Much as a shock wave precedes a supersonic airplane, astronomers think that a "termination shock" occurs near the edge of the solar system. This is a region where the speed of the solar wind drops dramatically as the wind brakes as it mixes with the interstellar medium, and where the density of ionized particles increases many times. It is also a region where some ions from the interstellar medium, relics of previous generations of stars, manage to diffuse through the edge of the Solar System and are accelerated tremendously.
Using an instrument on Voyager 1 called the low energy charged particle detector, Lanzerotti and his colleagues found evidence of all three effects. They saw a hundred-fold increase in the number of charged particles detected during a six-month period starting in August 2002; they deduced that the speed of the solar wind had dropped by a factor of seven; and they detected ions that came from beyond the Solar System.
"When we saw all that, we were pretty sure that we had reached the termination shock," Lanzerotti said.
Other members of the scientific team were Stamatios Krimigis (team leader), Robert Decker and Edmond Roelof of Johns Hopkins University; George Gloeckler, Douglas Hamilton and Matthew Hill of the University of Maryland; and Thomas Armstrong of the University of Kansas.
As the team analyzed its data from Voyager 1, it noticed something strange. It seemed that after six months, in early 2003, the termination shock region moved outwards, possibly as a result of increased solar activity. Scientists postulate that the heliosphere is a dynamic entity, which expands and contracts with the Sun's 11-year activity cycle.
"Solar eruptions must have caused the solar wind to pick up speed," said Lanzerotti. "That forced the heliosphere to expand outwards, and the termination shock must have moved outwards as well. Voyager 1 will probably encounter it again."
The team expects to get confirming data from a similar detector on Voyager 2, which is expected to follow Voyager 1 to the edge of the Solar System. The Voyager probes, among NASA's most successful spacecraft, are expected to provide data until approximately 2020, when they will exhaust their power supply from nuclear isotopes and drift off into space."Meanwhile, they will continue to provide a treasure trove of wonderful, sometimes unanticipated data about the far reaches of the Solar System and push the frontiers of our knowledge," Lanzerotti said.
This transit is a warmup for the June 8, 2004, transit of Venus. It
will be the first transit of Venus since 1882. Images of that transit
of Venus appear in the text. See
See also http://www.transitofvenus.org.
May 7, 2003, transit of Mercury:
A TRACE combination image, composited from over 5 hours of
observations in an extreme ultraviolet-wavelength:
A TRACE movie in an extreme-ultraviolet wavelength:
A TRACE movie in white light, with vignetting limiting the view to a
small region of the Sun by defining a circular lower edge to the field
A ground-based image by Philippe Jacquot of Annecy, France
A movie from the Global Oscillation Network Group (GONG):
A composite image from the Udaipur, India, GONG site, carefully
co-registered so that the overall Sun stayed steady. The solar
rotation blurred out the sunspots:
A ground-based composite white-light image by D. Dierick:
The DPS fully supports the plan for Solar System exploration just released by the National Research Council "New Frontiers in the Solar System: An Integrated Exploration Strategy". The DPS was actively involved in the Survey, providing ad-hoc reports written by its members as input to the NRC Survey Panels. The Survey provides a science community consensus on priorities for planetary missions and ground-based research for the next decade.
The key overall recommendations for non-Mars planetary missions are
1) maintenance of the Discovery program of low-cost (total mission cost less than $325M) missions at a flight rate of one every 18 months,
2) start of a New Frontiers line of medium-cost (less than $650M) competitively procured missions to be implemented as in the Discovery program, but selected from a prioritized list provided by the Survey, with a flight rate of about one every 3 years, and
3) one large-cost mission (greater than $650M) per decade.
The recommended large-cost mission is the Europa Geophysical Explorer, a version of the JPL Europa Orbiter concept. The recommended medium-cost New Frontiers missions are in priority order 1) KBO/Pluto Explorer, 2) Lunar South Polar Aitken Basin Sample Return, 3) Jupiter Polar Orbiter with Probes, 4) Venus In-Situ Explorer, and 5) Comet Surface Sample Return. The prioritized list of New Frontiers missions includes more than three missions to provide flexibility for technology and budgetary developments over the next ten years. In addition to the Discovery program of low-cost missions, the Survey recommends extension of the Cassini mission beyond its prime mission termination in 2007.
The Survey contains a separate set of prioritized recommendations for the Mars Exploration Program. After the launch of the Mars Reconnaissance Orbiter in 2005, there are two recommendations for the low-cost category of missions 1) a Mars Scout program of competitively procured missions implemented in the same manner as Discovery, with a flight rate of one Scout launch at every other Mars opportunity (one every 52 months) beginning in 2007, and 2) a Mars upper atmosphere orbiter. In the medium class category, the recommendations are for a Mars Smart Lander launch in 2009 and a Mars Long-lived Lander Network that could be implemented by international cooperation. The Survey recommends that these missions be implemented in a manner to build towards a Mars Sample Return mission early in the next decade. The Lunar South Polar Aitken Basin Sample Return mission should also be implemented in a manner to provide appropriate technological development for a Mars Sample Return.
There are also recommendations on fundamental research and analysis including a gradual increase in grant programs, recommendations on mission data analysis, the Deep Space Network, and technology development with an endorsement of the nuclear power and propulsion technologies initiative, and recommendations on ground-based support programs including a recommendation to share development and operations of a Large Synoptic Survey Telescope with the NSF. Implementation of the recommendations in this Survey would provide for a broad, integrated program of scientific exploration throughout the Solar System and enable new scientific discoveries addressing some of the most compelling scientific questions in planetary science.
The Division for Planetary Sciences of the American Astronomical Society endorses this report and looks forward to seeing its provisions implemented.
The full report is posted at http://www.nap.edu and has been posted at the community decadal website: http://www.aas.org/dps/decadal/
The DPS is the world's largest professional organization dedicated to the exploration of the Solar System.
The ozone hole is there all the time.
The ozone hole is in Antarctica and opens each year during the Antarctic springtime.
Antartica is the continent around the South Pole.
Note the spelling: the Arctic is in the north, and the second of those "c"'s remains in "Antarctica."
Foucault made daguerreotypes of the sun and the solar spectrum in 1844-45, within 5 years of Daguerre's invention of his type of photography. From an exhibition at L'Observatoire de Paris, we see his pendulum pictured in popular magazines and see one of his mechanisms for keeping the pendulum moving. We also see some of his daguerreotypes.
You can view satellite photos for most places in the U.S. and many places elsewhere. For urban areas, you can even specify a street address.
Home page: http://www.globexplorer.com/
Microsoft has a similar site ( http://terraserver.microsoft.com), but Globexplorer.com is easier to use.
See the movie at http://svs.gsfc.nasa.gov/~gshirah/toms/
General information on volcanoes:
Includes a list of recent eruptions and all the eruptions that have killed more than 500 people!
NASA's Observatorium is a public access site for Earth and space data.
View of the Earth from the NEAR spacecraft as it passed the Earth in January 1998 along with earlier views of the asteroid Mathilde are available.
On Saturday night, November 8-9, 2003, the full Moon will pass through the Earth's shadow for skywatchers throughout the Americas, Europe, and Africa, and in parts of Asia. For the Americas, this will be the second lunar eclipse of 2003; the first took place the night of May 15-16.
But the total phase of November's eclipse will be unusually brief, lasting only 25 minutes as the Moon skims barely inside the southern edge of our planet's dark shadow.
Skywatchers in eastern North America will see the entire eclipse during dark evening hours. Those living in the western half of North America will find the eclipse already in progress as the Moon rises around sunset.
All of Europe and most of Africa will see the eclipse in its entirety much later Saturday night. Observers in eastern and southern Africa, the Middle East, and southern Asia will see the eclipsed Moon set around sunrise on Sunday morning.
|Moon enters penumbra||
|First shading visible?||
|Partial eclipse begins||
|Total eclipse begins||
|Total eclipse ends||
|Partial eclipse ends||
|Last shading visible?||
|Moon leaves penumbra||
A total lunar eclipse occurs when the Sun, Earth, and Moon form a nearly straight line in space, so that the full Moon passes through Earth's shadow. Unlike a solar eclipse, which requires special equipment to observe safely, you can watch a lunar eclipse with your unaided eyes. Binoculars or a small telescope will enhance the view dramatically.
As the Moon moves into the outer fringe, or penumbra, of Earth's shadow, it will fade very slightly -- imperceptibly at first. Only when the leading edge of the Moon is at least halfway into the penumbra is any shading visible at all.
The real show starts when the Moon's leading edge first enters the shadow's dark core, or umbra, and the partial eclipse begins. For the next hour and 34 minutes, more and more of the Moon will slide into dark shadow.
The total eclipse begins when the Moon is fully within the umbra. But it likely won't be blacked out. The totally eclipsed Moon should linger as an eerie dark gray or coppery red disk in the sky, as sunlight scattered around the edge of our atmosphere paints the lunar surface with a warm glow. This is light from all the sunrises and sunsets that are in progress around Earth at the time.
Each total lunar eclipse is different. Sometimes the Moon looks like an orange glowing coal, while at other times it virtually disappears from view. Its brightness depends on the amount of dust in the Earth's upper atmosphere at the time, which influences the amount of sunlight that filters around the Earth's edges.
Because the Moon passes just inside the umbra, totality will be very short and the Moon's southern edge, in particular, should remain fairly bright. After only 25 minutes the leading edge of the Moon will emerge back into sunlight, and the eclipse is again partial. In another hour and 33 minutes the last of the Moon emerges out of the umbra.
Details about this event, and the solar eclipse visible from Antarctica, Australia, and New Zealand on November 23-24, appear in the November 2003 issue of SKY & TELESCOPE magazine.
The next total eclipse of the Moon falls on May 4-5, 2004, and is visible from central and south Asia, the Middle East, and the eastern two-thirds of Africa. North Americans will see their next lunar eclipse on October 27-28, 2004.
SMART stands for Small Missions for Advanced Research and Technology. SMART-1 is testing electric propulsion, miniaturization, and other technologies. Among other things, it will search for ice in lunar craters at the South Pole from the spacecraft's eventual elliptical polar orbit, ranging from a perihelion of 300 km to an aphelion of 10,000 above the lunar surface. The ion propulsion engine is slow but steady, and it will take 16 months (compared with Apollo's 4 dfays) to get from the Earth to the Moon.http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=31407
Observations of the bright side of the Moon with NASA's Chandra X-ray Observatory have detected oxygen, magnesium, aluminum and silicon over a large area of the lunar surface. The abundance and distribution of those elements will help to determine how the Moon was formed.
"We see X-rays from these elements directly, independent of assumptions about the mineralogy and other complications," said Jeremy Drake of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass, at a press conference at the "Four Years with Chandra" symposium in Huntsville, Alabama.
"We have Moon samples from the six widely-space Apollo landing sites, but remote sensing with Chandra can cover a much wider area," continued Drake. "It's the next best thing to being there, and it's very fast and cost-effective.
The lunar X-rays are caused by fluorescence, a process similar to the way that light is produced in fluorescent lamps. Solar X-rays bombard the surface of the Moon, knock electrons out of the inner parts of the atoms, putting them in a highly unstable state. Almost immediately, other electrons rush to fill the gaps, and in the process convert their energy into the fluorescent X-rays seen by Chandra.
According to the currently popular "giant impact" theory for the formation of the Moon, a body about the size of Mars collided with the Earth about 4.5 billion years ago. This impact flung molten debris from the mantle of both the Earth and the impactor into orbit around the Earth. Over the course of tens of millions of years, the debris stuck together to form the Moon. By measuring the amounts of aluminum and other elements over a wide area of the Moon and comparing them to the Earth's mantle, Drake and his colleagues plan to help test the giant impact hypothesis.
"One early result," quipped Drake, "is that there is no evidence for large amounts of calcium, so cheese is not a major constituent of the Moon."
The same Chandra data have also solved a long-running mystery about X-rays from the dark side of the Moon, as reported by Brad Wargelin also of CfA. Wargelin discussed how data from the German Roentgen satellite (ROSAT) obtained in 1990 showed a clear X-ray signal from the dark side. These puzzling "dark-Moon X-rays" were tentatively ascribed to energetic electrons streaming away from the Sun and striking the lunar surface.
However, Chandra's observations of the energies of individual X-rays, combined with simultaneous measurements of the number of particles flowing away from the Sun in the solar wind, indicate that the X-rays only appear to come from the Moon. In reality they come from much closer to home.
"Our results strongly indicate that the so-called dark Moon X-rays do not come from the dark side of the Moon," said Wargelin. "The observed X-ray spectrum, the intensity of the X-rays, and the variation of the X-ray intensity with time, can all be explained by emission from Earth's extended outer atmosphere, through which Chandra is moving."
In the model cited by Wargelin and colleagues, collisions of heavy ions of carbon, oxygen and neon in the solar wind with atmospheric hydrogen atoms located tens of thousands of miles above the surface of Earth give rise to these X-rays. In the collisions, the solar ions capture electrons from hydrogen atoms. The solar ions then kick out X-rays as the captured electrons drop to lower energy states."This idea has been kicking around among a small circle of believers for several years supported by theory and a few pieces of evidence," said Wargelin. "These new results should really clinch it."
In 2003, both the Japanese Lunar-A spacecraft and the European Space Agency's "Small Missions for Advanced Research in Technology 1" (SMART-1) have long been scheduled for launch. Lunar A will not only map the moon but also drop two probes that will penetrate the lunar surface, carrying seismometers and equipment to measure heat flow.
To that pair of missions, and to a potential Chinese mission, a private American company called TransOrbital has received a license from NOAA and the US Departments of Defense and State to launch a spacecraft to the moon. ("How does a United States body like NOAA get the right to issue a license for anything to do with the Moon anyway" is an interesting question.)
TransOrbital's TrailBlazer spacecraft's main aim is to get public attention. Further, it will carry an HDTV camera to take high-resolution images with a resolution as high as 1 meter on the lunar surface. It is to be launched from the Baikonur Cosmodrome in Kazakhstan and is planned for 90 days of orbiting the moon. It is then to be crashed into the moon, carrying a time capsule as well as things people have paid to have crashed into the moon in that way.
The Lunar and Planetary Institute (LPI) has created a digital version of the "Lunar Orbiter Photographic Atlas of the Moon," published in 1971 and considered "the definitive reference manual to the global photographic coverage of the Moon." The site includes all 675 plates contained in the original work, digitally enhanced to increase photo quality. Visitors can view images by feature name, listed alphabetically or by descending latitude and longitude, or they can search by feature name, photo number, or coordinate range. Returns include a large thumbnail image, photo number, feature name, latitude and longitude, size, sun angle, spacecraft altitude, and medium photo center latitude and longitude. Students and general users may wish to consult the even easier to use Consolidated Lunar Atlas, which allows browsing by a long list of plates, thumbnails, or even better, an interactive image map.
"That's one small step for a man, one giant leap for mankind."
- Neil Armstrong
"Thin man ran; makes a large stride, left planet, pins flag on moon! On to Mars!"
Johns Hopkins University APL Press Release, March 29, 2002
The first mission to orbit the planet Mercury took a big step toward its scheduled March 2004 launch when NASA's MESSENGER project received approval to start building its spacecraft and scientific instruments.
MESSENGER - which stands for MErcury Surface, Space ENvironment, GEochemistry, and Ranging - passed a thorough four-day critical design review last week, during which a project advisory panel and NASA assessment team examined every detail of the mission and spacecraft design.
"The review was very successful," says Max R. Peterson, MESSENGER project manager at the Johns Hopkins University Applied Physics Laboratory (APL), Laurel, Md. "Both panels confirmed that our designs are sound and meet the mission's science and engineering requirements. We're ready to move to the next stage."
MESSENGER team members are building flight hardware now and will begin integrating parts on the spacecraft this November, Peterson says. After launch and a five-year journey through the inner solar system, MESSENGER will orbit Mercury for one Earth year, providing the first images of the entire planet and collecting information on the composition and structure of Mercury's crust, its geologic history, the nature of its thin atmosphere and active magnetosphere, and the makeup of its core and polar materials. While cruising to Mercury the spacecraft will fly past the planet twice - in 2007 and 2008 - snapping pictures and gathering data critical to planning the orbit study that begins in April 2009.
A key MESSENGER design element deals with the intense heat at Mercury. The sun is up to 11 times brighter than we see on Earth and surface temperatures can reach 450 degrees Celsius (about 840 degrees Fahrenheit), but MESSENGER's instruments will operate at room temperature behind a sunshield made of heat-resistant Nextel fabric. The spacecraft will also pass only briefly over the hottest parts of the surface, limiting exposure to reflected heat.
"The project is well on its way," says Dr. Sean C. Solomon, MESSENGER principal investigator from the Carnegie Institution of Washington (D.C). "Exploring the many mysteries of Mercury will help us to understand all of the terrestrial planets, including Earth. The team is eagerly looking forward to assembling and launching the spacecraft and to the first new data from the innermost planet."
In July 1999, NASA selected MESSENGER as the seventh mission in its innovative Discovery Program of lower-cost, highly focused space science investigations. APL manages the $286 million project for NASA's Office of Space Science and will build and operate the MESSENGER spacecraft.
MESSENGER Mission Web Site: http://messenger.jhuapl.edu NASA Discovery Program Web Site: http://discovery.nasa.gov
Mark Robinson has some reprocessed images of Mercury available on his web site
Mark Robinson has some reprocessed images of Mercury available on his web site
Boston University Press release, 5/26/00
Ever since Galileo first used a telescope in 1609, astronomers have tried to capture images of the surface of Mercury with a ground-based telescope. Now, a team of astronomers from Boston University released images revealing details of Mercury's surface in the May issue of The Astronomical Journal and at the American Geophysical Union in Washington, DC.
"More than a quarter-century ago, the Mariner 10 spacecraft flew past Mercury and for the first and only time transmitted satellite-based photos of half of the surface of the planet closest to the Sun.," says lead author Jeffrey Baumgardner, senior research associate in the Center for Space Physics at BU. "Capturing similar images from a ground-based telescope represents a significant milestone in advanced instrumentation," he adds.
The BU images, taken on August 29, 1998, at the Mt. Wilson Observatory in California, reveal surface markings similar to the bright craters and dark lunar mare found on the Moon. The BU images captured using a digital camera and stored on CD-ROMs for subsequent processing show never-before- seen-portions of Mercury.
Photographing Mercury is challenging because of the planet's proximity to the Sun. Mercury only has a few viewing times, before sunrise or shortly after sunset. At rare times when 'the seeing' is right, the air is clear and researchers are looking through less turbulence in Earth's atmosphere. Opportunities to photograph Mercury from space are also limited because light sensitive equipment, such as the Hubble Space Telescope, are not allowed to look at objects close to the Sun, such as Mercury or Venus. This restriction has been established to avoid the possibility of an accidental pointing error causing too much light to fall upon an instrument.
"The observations were made shortly after sunrise before the Sun's heating of the atmosphere distorted the images captured by the telescope," says Michael Mendillo, professor of astronomy at BU.
In order to obtain a clear photograph Baumgardner took images with very short exposures, 1/60th of a second, continuously for 90 minutes. "That comes to 340,000 pictures," Mendillo added. "The trick to getting a clear image was then to find the best ones, say 30 to 60, that could be added together by computer to create a time exposure of sufficient duration (.5 to 1 second) in order to capture detail on Mercury's surface."
Baumgardner and Research Associate Jody Wilson assisted by Mead Misic, a sophomore in the College of Engineering, all took part in the search for the perfect images. They developed sophisticated computer techniques to identify the best images with detail taken during rare instances of 'perfect seeing.'
"We captured multiple images of Mercury during these rare instances of 'perfect seeing,'" says Wilson. "and by combining these images, a unique photograph with details and clarity resulted. "
The Boston University team plans to make additional observations of Mercury this fall, even pushing the technique to try to image the planet's weak atmosphere. "Mercury has a thin atmosphere created by the ejection of atoms from its surface, a process that also occurs on our Moon," Mendillo explained. One of the chemical elements in Mercury's atmosphere is sodium, a gas somewhat easy to detect because it reflects sunlight very efficiently. "We hope to try our first sodium detection experiments this fall," Baumgardner said. "But that will first involve building a more sensitive detector system."
For more information, log on to
NASA Press Release
The first comprehensive mission to map pockmarked Mercury and a radical mission to excavate the interior of a comet have been selected as the next flights in NASA's Discovery Program.
The Mercury Surface, Space Environment, Geochemistry and Ranging mission, or Messenger, will carry seven instruments into orbit around the closest planet to the Sun. It will send back the first global images of Mercury and study its shape, interior and magnetic field. Dr. Sean Solomon of the Carnegie Institution, Washington, DC, will lead Messenger.
The Deep Impact mission will send a 1,100-pound (500- kilogram) copper projectile into comet P/Tempel 1, creating a crater as big as a football field and as deep as a seven-story building. A camera and infrared spectrometer on the spacecraft, along with ground-based observatories, will study the resulting icy debris and pristine interior material. Dr. Michael A'Hearn will lead Deep Impact from the University of Maryland in College Park.
Messenger, to be launched in spring 2004, will be NASA's first mission to Mercury since the Mariner 10 flybys in 1974 and 1975, which provided information on only half the planet. Its challenging flight plan begins with two Venus flybys, then two Mercury flybys in January and October 2008 and a subsequent orbital tour of Mercury beginning in September 2009.
Among Messenger's goals will be to discover whether Mercury has water ice in its polar craters. The cost of Messenger to NASA is $286 million. It will be built and managed by the Johns Hopkins University's Applied Physics Laboratory, Laurel, MD. Further information about the mission is available on the Internet at: http://sd-www.jhuapl.edu/MESSENGER
Deep Impact will be launched in January 2004 toward an explosive July 4, 2005, encounter with P/Tempel 1. It will use a copper projectile because that material can be identified easily within the spectral observations of the material blasted off the comet by the impact, which will occur at an approximate speed of 22,300 mph (10 kilometers per second.) The total cost of Deep Impact to NASA is $240 million. Deep Impact will be managed by NASA's Jet Propulsion Laboratory in Pasadena, CA, and built by Ball Aerospace in Boulder, CO.
NASA selected these missions from 26 proposals made in early 1998. The missions must be ready for launch no later than Sept. 30, 2004, within the Discovery Program's development cost cap of $190 million in Fiscal 1999 dollars over 36 months and a total mission cost of $299 million.
The Discovery Program emphasizes lower-cost, highly focused scientific mission. NASA has developed six other Discovery Program missions. Two have completed their primary missions, two are operational and two more are under development:
-- The Lunar Prospector orbiter has mapped the Moon's composition and gravity field for the past 18 months. It will complete its highly successful mission on July 31, when it is sent on a controlled impact into a crater near the south lunar pole. Scientists hope to observe a resulting plume of water vapor that would help confirm the presence of water ice in some of the Moon's permanently shadowed craters. In 1997, the Mars Pathfinder lander, carrying a small robotic rover named Sojourner, landed successfully on Mars and returned hundreds of images and thousands of measurements of the Martian environment.
-- The Near Earth Asteroid Rendezvous (NEAR) spacecraft is scheduled to enter orbit around the asteroid Eros in February 2000, after a problem with its initial attempt to do so early this year. The Stardust mission to gather samples of comet dust and return them to Earth was launched in February 1999.
-- The Genesis mission to gather samples of the solar wind and return them to Earth and the Comet Nucleus Tour (CONTOUR) mission to fly closely by three comets are being prepared for launch in January 2001 and June 2002, respectively.
Transits of Venus, 2004:http://www.phys.uu.nl/~bassa/index_miscell.htm
Many people on this list are looking forward to the upcoming 2004 and 2012 transits of Venus with great anticipation. I recently prepared a presentation on these two events which I have just posted on the web:
Of particular interest is the figure which shows the path of Venus across the Sun's disk during both transits:
Note that Venus will be about 1/32 the diameter of the Sun and should be visible to the unaided (but solar filtered) eye if your eyesight is excellent.
The global zones of visibility of the 2004 transit are illustrated in:
Similarly, the global zones of visibility of the 2012 transit are illustrated in:
Note that higher resolution versions of these figures are all available through links from the first URL address in this message.Furthermore, this primary web page has links to tables of local circumstances for nearly two hundred cities for each transit.
And speaking of transits, the next transit of Mercury is less than a year away (2003 May 07) and occurs just three weeks before the Iceland/Scotland sunrise annular eclipse (2003 May 31). The transit will be best seen from Europe, Africa and Asia. You can read all about it in my article in the Royal Astronomical Society of Canada's Observers Handbook for 2003. There is a map showing the global visibility as well as Mercury's path across the Sun. A table gives local circumstances for dozens of cities around the world. The entire article is posted online at:
Fifteen days after the launch of Mars Express, Europe has reaffirmed its trust in Soyuz: next stop Venus in 2005!http://sci.esa.int/content/news/index.cfm?aid=64&cid=4450&oid=32411
ESA Press Release, November 5, 2002
ESA's Science Programme Committee (SPC) gave the final go-ahead for
the Venus Express mission. The SPC unanimously confirmed its strong
will to bring the mission to realisation. Launch is expected in 2005.
July 30, 2002
The European Space Agency has decided to start work on Venus Express for
launch in late 2005. To save money, it will use the same basic type of
vehicle as Mars Express.
Royal Astronomical Society Press Notice, April 3, 2002
The European Space Agency is planning its first mission to unveil the mysteries of Earth's cloud-shrouded sister planet, Venus. On Wednesday 10 April 2002, Professor Fred Taylor (University of Oxford) explained to the UK National Astronomy Meeting why European scientists are hoping to be on board the Venus Express in 2005.
Venus, the Earth's nearest planetary neighbour, is remarkably similar in size and mass to our own world. However, its atmosphere and climate could hardly be more different. The reasons for these contrasts are proving difficult to understand. Scientists still do not know, for example, the details of the greenhouse effect on Venus, which keeps the surface hot enough for molten metal to flow, despite the fact that Venus absorbs less heat from the Sun than the Earth does.
Venus and Earth have also evolved quite differently. Venus has vast, smooth plains, no continents and extensive volcanic activity that produces dense cloud layers with an exotic, sulphur-rich composition.
Most puzzling of all is the atmospheric circulation which features hurricane force winds at high levels that sweep around Venus in just four days - remarkably rapid for a planet that only rotates once every 243 Earth days.
"The planet's weather systems and climate characteristics cannot be understood by comparison with Earth," said Professor Taylor. "The failure of extrapolated terrestrial models to account for Venus' behaviour has wide implications in fields ranging from solar system evolution to climate forecasting on Earth."
Venus Express is proposed to be launched on a direct trajectory to Venus with a Soyuz-Fregat rocket from Baikonur in November 2005. After a flight of about 150 days, it will brake into a highly elliptical 5-day orbit around Venus. The spacecraft will then be manoeuvred to its operational polar orbit between 250 km and 45,000 km above the planet where, for two Venus years - equivalent to 450 Earth days - it will study the atmosphere, the surface and the plasma environment of Venus.
In order to lower costs, Venus Express is to be based on the European Space Agency's Mars Express spacecraft (which is scheduled for launch in summer 2003) and it will use seven flight spare experiments from Mars Express and the Rosetta comet chaser.
"Venus Express is a strong candidate to be part of the next wave of Venus exploration, including Japanese and probably American space missions, which will probe the environment of this mysterious planet," concluded Professor Taylor.
Though the Viking Landers in the 1970s observed the shadow of one Mars' two moons, Phobos, moving across the landscape, and Mars Pathfinder in 1997 observed Phobos emerge at night from the shadow of Mars, no previous mission has ever directly observed a moon pass in front of the sun from the surface of another world.
The current rovers began their eclipse-watching campaign this month. Opportunity's panoramic camera caught Mars' smaller moon, Deimos, as a speck crossing the disc of the sun on March 4. The same camera then captured an image of the larger moon, Phobos, grazing the edge of the sun's disc on March 7.
Rover controllers at NASA's Jet Propulsion Laboratory (JPL), Pasadena, Calif., are planning to use the panoramic cameras on both Opportunity and Spirit for several similar events in the next six weeks. Dr. Jim Bell of Cornell University, Ithaca, N.Y., lead scientist for those cameras, expects the most dramatic images may be the one of Phobos planned for March 10.
"Scientifically, we're interested in timing these events to possibly allow refinement of the orbits and orbital evolution of these natural satellites," Bell said. "It's also exciting, historic and just plain cool to be able to observe eclipses on another planet at all," he said.
Depending on the orientation of Phobos as it passes between the sun and the rovers, the images might also add new information about the elongated shape of that moon.
Phobos is about 27 kilometers long by about 18 kilometers across its smallest dimension (17 miles by 11 miles). Deimos' dimensions are about half as much, but the pair's difference in size as they appear from Mars' surface is even greater, because Phobos flies in a much lower orbit.
The rovers' panoramic cameras observe the sun nearly every martian day as a way to gain information about how Mars' atmosphere affects the sunlight. The challenge for the eclipse observations is in the timing. Deimos crosses the sun's disc in only about 50 to 60 seconds. Phobos moves even more quickly, crossing the sun in only 20 to 30 seconds.
Scientists use the term "transit" for an eclipse in which the intervening body covers only a fraction of the more-distant body. For example, from Earth, the planet Venus will be seen to transit the sun on June 8, for the first time since 1882. Transits of the sun by Mercury and transits of Jupiter by Jupiter's moons are more common observations from Earth.
From Earth, our moon and the sun have the appearance of almost identically sized discs in the sky, so the moon almost exactly covers the sun during a total solar eclipse. Because Mars is farther from the sun than Earth is, the sun looks only about two-thirds as wide from Mars as it does from Earth. However, Mars' moons are so small that even Phobos covers only about half of the sun's disc during an eclipse seen from Mars.
JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover project for NASA's Office of Space Science, Washington. Images and additional information about the project are available from JPL at:Images of those two events are available online at:
For further information, see
Visit our special Mars Express website.
The two dominant dark swatches seen on this part of the planet are classical regions labeled by early Mars observers. The "shark-fin" shape to the right is Syrtis Major. The horizontal lane to the left is Sinus Meridani. One of NASA's Mars Exploration Rovers, named "Opportunity," will land at the western end of this region in January 2004.
The picture shows that it a relatively warm summer on Mars as evident in the lack of water-ice clouds at mid latitude, and the receding southern polar cap. Ice on the rugged topography gives a somewhat ragged, scalloped look. Up north, at the top of the disk where it is Martian winter, a frigid polar hood of clouds covers the northern polar cap.
Even in the relatively balmy southern hemisphere, daytime highs are just above freezing in the Hellas impact basin, the circular feature near the image center. Hellas is nearly 5 miles deep (8 km). It is Mars' equivalent of Death Valley California - except the entire planet is much drier than even Death Valley. Having a diameter of 1,100 miles (1,760 km), Hellas was formed when an asteroid slammed into Mars billions of years ago. Many summer dust storms originate in this basin, though it is remarkably clear of dust in this Hubble image.
Mars and Earth have a "close encounter" about every 26 months. These periodic encounters are due to the differences in the two planets' orbits. Earth goes around the Sun twice as fast as Mars, lapping the red planet about every two years. Both planets have elliptical orbits, so their close encounters are not always at the same distance. In its close encounter with Earth in 2001, for example, Mars was about 9 million miles farther away. Because Mars will be much closer during this year's close approach, the planet appears 23 percent bigger in the sky.
This photograph is a color composite generated from observations taken with blue, green, and red, filters. The resolution is 8 miles (12 km) per pixel.
Credit: NASA, J. Bell (Cornell U.) and M. Wolff (Space Science Inst.) Additional image processing and analysis support from: K. Noll and A. Lubenow (STScI); M. Hubbard (Cornell U.); R. Morris (NASA/JSC); P. James (U. Toledo); S. Lee (U. Colorado); and T. Clancy, B. Whitney and G. Videen (Space Science Inst.); and Y. Shkuratov (Kharkov U.)
Electronic images and additional information are available at
Images from the Mars Orbiter Camera aboard NASA's Mars Global Surveyor capture a faint yet distinct glimpse of the elusive Phobos, the larger and innermost of Mar s' two moons. The moon, which usually rises in the west and moves rapidly across the sky to set in the east twice a day, is shown setting over Mars' afternoon horizon.The images are available on the Internet at:
Phobos is so close to the martian surface (less than 6,000 kilometers or 3,728 miles away),=20 it only appears above the horizon at any instant from less than a third of the planet's surface. From the areas where it is visible, Phobos looks only half as large as Earth's full moon. Like our satellite, it always keeps the same side facing Mars. The tiny moon is also one of the darkest and mostly colorless (dark grey) objects in the solar system, so for the color image two exposures were needed to see it next to Mars. The faint orange-red hue seen in the wide-angle image is a combination of the light coming from Mars and the way the camera processes the image.
On June 20, NASA launched one of its rovers to Mars, where it is to arrive in January 2004. On launch, it was named "Spirit." The second rover, strangely named "Opportunity," is to be launched in a couple of weeks. These two rovers, each the size of a golf course, is to wander around the Martian surface, covering a much larger area than the Mars. Pathfinder did five years ago. Each carries a wide-field camera, a close-up camera, and a drill to penetrate the Martian surface. Dust on the solar panels may limit their usability to several months, once they land. Their goal is to find signs of water on Mars from studying the rocks and the minerals in them.
Last week, the European Space Agency launched its Mars Express, which carries the Beagle 2 lander. It is working fine.
The European Space Agency's Mars Express, carrying the Beagle 2 lander that will search for life (Beagle 1 was Darwin's ship, the Beagle), was launched on June 2, 2003. It will be at Mars at Christmastime.
On 2 June 2003, the first European mission to Mars will be launched. It will also be the first European mission to any planet. Mars Express has been designed to perform the most thorough exploration ever of the Red Planet. It has the ambitious aim of not only searching for water, but also understanding the 'behaviour' of the planet as a whole. However, the most ambitious aim of all may be that Mars Express is the only mission in more than 25 years that is daring to search for life.
ESA Press Release, September 3, 2002
Of all missions sent to Mars only one, the Viking 26 years ago, has dared to search for life. Its only conclusive result was that finding proof of extraterrestrial life proved to be much harder than expected. Second attempts never followed. Until now. ESA's Mars Express, the next mission to the Red Planet and the first European one, has an ambitious goal. To be launched in 2003, Mars Express will be the first spacecraft after Viking to search for direct and indirect evidence for past or present life on Mars. This time, scientists are equipped with more knowledge and insight in how to detect Martian life. The chances of success look very good.
ESA's Mars Express is to be launched in May/June 2003 for arrival at
Mars in December of that year. It is to carry the Beagle 2 spacecraft
to look for life on Mars. (Beagle 1 was Darwin's ship "Beagle.")
ESA Press Release, 7/21/02
What is the fastest Ferrari's distinctive red paint has ever travelled? Next year it will be 10800 km/h! Mars Express, to be launched in May/June 2003, the first European spacecraft to visit the Red Planet, will be speeding on its way accompanied by the very essence of Ferrari: a sample of its distinctive red paint.
JPL/Arizona State U. Press Release, May 29, 2002
There are tantalizing indications emerging from the thousands of infrared images taken so far by NASA's Mars Odyssey spacecraft that Mars experienced a series of environmental changes during active geological periods in its history.
"We knew from Mars Global Surveyor that Mars was layered, but these data from Odyssey are the first direct evidence that the physical properties of the layers are different. It's evidence that the environment changed over time as these layers were laid down," said Dr. Philip Christensen, principal investigator for Odyssey's camera system and professor at Arizona State University, Tempe. "The history of Mars is staring us in the face in these different layers, and we're still trying to figure it all out."
"I expect that the primitive geologic maps of Mars that we have constructed so far will all be redrawn based on Odyssey's new information," said Dr. R. Stephen Saunders, Odyssey's project scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif.
A mosaic of daytime infrared images of the layered Terra Meridiani region shows a complex geology with craters and eroded surfaces, exposing at least four distinct layers of rock. Though the image does not include the infrared "colors" of the landscape (showing surface mineral composition), it does map the temperatures of the features, with surprising results.
"With these temperature data, Odyssey has already lived up to our expectations, but Mars, in fact, has itself exceeded our expectations," said Christensen. "It would have been entirely possible for the rocks of Mars to have been very similar and thus give us all the same temperatures, but Mars has a more interesting story to tell and we have the data to tell it."
The images can be seen at: http://www.jpl.nasa.gov/images/mars/index.html
"When we look at these distinct layers we see that the temperatures are very different, indicating that there are significant differences in the physical properties of the rock layers," Christensen said.
The differences in surface temperature could be caused by the fundamental differences in either the size of the rock fragments in the layer, the mineral composition or the density of the layers.
Odyssey's imaging team is working on fully processing the infrared images, a complex and difficult task. When finished, the data will help them test some important theories about what causes the layers on Mars by examining the mineral composition of the specific layers. Plausible explanations include a history of volcanic activity depositing layers of lava and volcanic ash; a history of different processes that created the layers through wind and water; or a history of climate change that varied the nature of the materials deposited.
Christensen theorizes that the layers are caused not by surface effects, but by changes in the planet's subsurface water table. The presence or absence of water and the minerals carried in it can significantly affect how sediment particles are cemented together. With no clear evidence for surface water, precipitation or runoff, Christensen believes that changes in levels of underground water percolating through layers of buried sediments could account for differences in rock composition between layers. More complete infrared data will help to confirm or disprove this and many other hypotheses concerning Mars' geology.
"Looking at craters, we're seeing new distributions of rock on the surface that are helping us understand events in martian geology, and we are getting our first glimpses of 'color' infrared images, which will help us precisely determine the composition of the Mars' surface. This is just the beginning," Christensen said.
Additional information about the 2001 Mars Odyssey is available on the Internet at: http://mars.jpl.nasa.gov/odyssey/.
Arizona State University Press Release, March 27, 2002
Need to get away to someplace exotic? Mars is now open for daily sightseeing.
Beginning March 27, 2002, recent images of Mars taken by the Thermal
Emission Imaging System on NASA's Mars Odyssey spacecraft will be available
to the public on the Internet. A new, "uncalibrated" image taken by the
visible light camera will be posted at 10 A.M. EST daily, Monday through
Friday. The pictures can be viewed and downloaded at:
The images will show 22 kilometer-wide strips of the martian surface at a resolution of 18 meters. Though the images will not yet be fully calibrated for scientific use, they give the public an unprecedented opportunity to get a close look at many of Mars' unusual geological features. The visible light camera's resolution is about eight to 16 times better than most of the images taken by NASA's Viking missions, which completed the first global map of the martian surface. "We want to generate a steady flow of images so we can share some of the excitement of what we're seeing with the public," said Greg Mehall, THEMIS mission manager at Arizona State University. "We're seeing a lot of very interesting things, since much of Mars has never been viewed so closely before."
Though the posted images have undergone only minimal image processing, the team wanted to share them with the public as soon as possible. "They're still pretty spectacular to look at," Mehall said. "And we want people to feel they are getting a first look at the images with us."
THEMIS began mapping Mars from an orbit of 420 kilometers in mid-February, taking images in both infrared and visible light The instrument is expected to take as many as 15,000 visible light images through the course of the mission.
The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the 2001 Mars Odyssey mission for NASA's Office of Space Science in Washington. Investigators at Arizona State University in Tempe, the University of Arizona in Tucson and NASA's Johnson Space Center, Houston, operate the science instruments. Additional science partners are located at the Russian Aviation and Space Agency and at Los Alamos National Laboratories, New Mexico.
Lockheed Martin Astronautics, Denver, is the prime contractor for the
project, and developed and built the orbiter. Mission operations are
conducted jointly from Lockheed Martin and from JPL. Additional information
about the 2001 Mars Odyssey is available on the Internet at:
NASA's 2001 Mars Odyssey gave mission managers a real treat this Halloween with its first look at the Red Planet. It's a thermal infrared image of the Martian southern hemisphere that captures the polar carbon dioxide ice cap at a temperature of about minus 120 C (minus 184 F).
The spacecraft first entered orbit around Mars last week after a six-month, 285 million-mile journey.
The image, taken as part of the calibration process for the instrument, shows the nighttime temperatures of Mars, demonstrating the "night-vision" capability of the camera system to observe Mars, even when the surface is in darkness.
"This spectacular first image of Mars from the 2001 Mars Odyssey spacecraft is just a hint of what's to come," said Dr. Ed Weiler, Associate Administrator for Space Science at NASA Headquarters in Washington. "After we get Odyssey into its final orbit it will be much closer to Mars than when it took this image, and we'll be able to tell whether or not there are any hot springs on Mars, places where liquid water may be close to the surface. If there are any such locations they would be places we might like to explore on future missions."
The image covers a length of more than 6,500 kilometers (3,900 miles), spanning the planet from limb to limb, with a resolution of approximately 5.5 kilometers per pixel (3.4 miles per pixel), at the point directly beneath the spacecraft.
The spacecraft was about 22,000 kilometers (about 13,600 miles) above the planet looking down toward the south pole of Mars when the image was taken.
It is late spring in the Martian southern hemisphere. The extremely cold, circular feature shown in blue is the Martian south polar carbon dioxide ice cap , which is more than 900 kilometers (540 miles) in diameter at this time and will continue to shrink as summer progresses. Clouds of cooler air blowing off the cap can be seen in orange extending across the image.
JPL manages the 2001 Mars Odyssey mission for NASA's Office of Space Science. The thermal-emission imaging system was developed at Arizona State University, Tempe, with Raytheon Santa Barbara Remote Sensing, Santa Barbara, Calif. Lockheed Martin Astronautics, Denver, is the prime contractor for the project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.
The Mars Odyssey image is available on the Internet at:
Flight controllers for NASA's 2001 Mars Odyssey mission report the spacecraft is in excellent health and is in a looping orbit around Mars of 18 hours and 36 minutes.
"Odyssey flawlessly achieved last night's one-time critical event of Mars orbit insertion. Hundreds and hundreds of things had to go right, and they did," said Matt Landano, Mars Odyssey project manager at NASA's Jet Propulsion Laboratory. "We are all excited about our success and I am proud of all the members of our team."
The navigation proved to be equally precise. "We were aiming for a point 300 kilometers (186.5 miles) above Mars and we hit that point within one kilometer (.6 miles)," reports Bob Mase, the Mars Odyssey lead navigator at JPL. "Because of the excellent main engine burn, we will not need to do any more maneuvers to adjust the orbit before we begin aerobraking on Friday."
In the weeks and months ahead, the spacecraft will be literally surfing the waves of the martian atmosphere, in a process called aerobraking, which will reduce the long elliptical orbit into a shorter, 2-hour circular orbit of approximately 400 kilometers (about 250 miles) altitude.
This morning, the team turned on the electronics for the gamma ray spectrometer subsystem and began taking data with the high-energy neutron detector and the neutron spectrometer instruments. These detectors may help scientists locate water near
On Sunday, Oct. 28, scientists will take the first picture with the thermal emission imaging system. That image is expected to be a wide-angle view of the southern hemisphere taken when Odyssey is farthest away from Mars. The primary science mission will begin in January 2002.
A pair of eagle-eyed NASA spacecraft -- the Mars Global Surveyor (MGS) and Hubble Space Telescope -- are giving amazed astronomers scientists a ringside seat to the biggest global dust storm seen on Mars in several decades.
The Martian dust storm, larger by far than any seen on Earth, has raised a cloud of dust that has engulfed the entire planet for the past three months. As the Sun warms the airborne dust the upper atmospheric temperature has been raised by about 80 degrees Fahrenheit. This abrupt onset of global warming in Mars' thin atmosphere is happening at the same time as the planet's surface has chilled precipitously under the constant dust shroud.
"This is an opportunity of a lifetime," said Hubble observer James Bell of Cornell University in Ithaca, NY. "We have a phenomenal, unprecedented view from these two spacecraft."
"The beauty of Mars Global Surveyor is that we have almost two Martian years of continuous coverage, and this is the first time during the mission that we have seen such a storm," added Richard Zurek of the Jet Propulsion Laboratory in Pasadena, CA.
This storm is being closely watched by the team operating NASA's 2001 Mars Odyssey spacecraft, which is heading toward a rendezvous with the Red Planet later this month. The Odyssey team plans to "toe-dip" its way into the Martian atmosphere, gradually deepening its pass through the atmosphere until the desired drag levels are found. A warm atmosphere "puffs up," creating more drag on the spacecraft.
The Thermal Emission Spectrometer on the Global Surveyor has been tracking the blooming dust storm by measuring temperature changes that trace the amount and location of dust in the atmosphere. Both Hubble and MGS caught the storm erupting in late June, which was unusually early in the spring of the Martian Northern Hemisphere compared to previous large storms. Hubble doesn't have continuous Mars coverage, but does show the whole planet in a single snapshot and shows the full range of dust activity from sunrise to sunset.
Planetary scientists photograph the entire planet every day using the Global Surveyor's Mars Orbiter Camera. This has allowed them to pinpoint the actual location of places where dust was being raised, and see it migrate and interact with other Martian weather phenomena and surface topography. This has also provided them an unprecedented, detailed look at how storms start and "blossom" across the orange, arid planet.
"What we have learned is that this is not a single, continuing storm, but rather a planet-wide series of events that were triggered in and around the Hellas Basin," said Mike Malin of Malin Space Science Systems, Inc., San Diego, lead investigator on the camera. "What began as a local event stimulated separate storms many thousands of kilometers away. We saw the effects propagate very rapidly across the equator -- something quite unheard of in previous experience -- and move with the Southern Hemisphere jet stream to the east."
"By the time the first tendrils of dust injected into the stratosphere by the initial events circumnavigated the Southern Hemisphere, which took about a week, separate storms were raging in three main centers. The most intriguing observation is that the regional storm in Claritas/Syria has been active every day since the end of the first week of July," said Malin.
After three months, the storm is beginning to wane. The planet's shrouded surface has cooled, and this allowed the winds to die down and the fine dust to begin settling. However, Mars is approaching the closest point of its orbit to the Sun. Once the atmosphere begins to clear, the return of unfiltered solar radiation may trigger additional high winds and kick up the dust all over again. This one-two punch has been seen in previous Mars storms for centuries.
"Understanding global dust storms, such as that which we have witnessed this year, is a vital part of the science goals of the Mars Exploration Program," said James Garvin, NASA's lead scientist for Mars exploration, NASA Headquarters, Washington. "Such extreme climate events could potentially provide clues to how climate changes operate on Mars, now and in the past, and provide linkages to the record of sediments on the planet."
The Space Telescope Science Institute (STScI) is operated by the Association of Universities for Research in Astronomy, Inc. (AURA), for NASA, under contract with the Goddard Space Flight Center, Greenbelt, MD. The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency (ESA). The Mars Global Surveyor is managed by the Jet Propulsion Laboratory, a division of the California Institute of Technology, for NASA's Office of Space Science, Washington, D.C.
Electronic images, animation, illustrations, and additional
information are available on the Internet at:
http://hubble.stsci.edu/go/news and via links in
[NASA Press Release, December 4, 2000]
In what ultimately may be their most significant discovery yet, Mars scientists say high-resolution pictures showing layers of sedimentary rock paint a portrait of an ancient Mars that long ago may have featured numerous lakes and shallow seas.
"We see distinct, thick layers of rock within craters and other depressions for which a number of lines of evidence indicate that they may have formed in lakes or shallow seas. We have never before had this type of irrefutable evidence that sedimentary rocks are widespread on Mars," said Dr. Michael Malin, principal investigator for the Mars Orbiter Camera on NASA's Mars Global Surveyor spacecraft at Malin Space Science Systems (MSSS), San Diego, CA. "These images tell us that early Mars was very dynamic and may have been a lot more like Earth than many of us had been thinking."
Such layered rock structures where there were once lakes are common on Earth. The pancake-like layers of sediment compressed and cemented to form a rock record of the planet's history.
The regions of sedimentary layers on Mars are spread out and scattered around the planet. They are most common within impact craters of Western Arabia Terra, the inter-crater plains of northern Terra Meridiani, the chasms of the Valles Marineris, and parts of the northeastern Hellas Basin rim. The scientists compare the rock layers on Mars to features seen in the American Southwest, such as the Grand Canyon and the Painted Desert of Arizona.
"We caution that the Mars images tell us that the story is actually quite complicated and yet the implications are tremendous. Mars has preserved for us, in its sedimentary rocks, a record of events unlike any that occur on the planet today," said Dr. Ken Edgett, staff scientist at MSSS. "This is changing the way we think about the early history of Mars -- a time perhaps more than 3.5 billion years ago."
"On Earth, sedimentary rocks preserve the surface history of our planet, and within that history, the fossil record of life. It is reasonable to look for evidence of past life on Mars in these remarkably similar sedimentary layers," said Malin. "What is new in our work is that Mars has shown us that there are many more places in which to look, and that these materials may date back to the earliest times of Martian history."
Malin added, "I have not previously been a vocal advocate of the theory that Mars was wet and warm in its early history. But my earlier view of Mars was really shaken when I saw our first high- resolution pictures of Candor Chasma. The nearly identically thick layers would be almost impossible to create without water."
As an alternative to lakes, Malin and Edgett suggest that a denser atmosphere on early Mars could have allowed greater amounts of windborne dust to settle out on the surface in ways that would have created the sedimentary rock.
"We have only solved one little piece of a tremendous puzzle," Malin said. "There is no illustration on the box to show us what it is supposed to look like when it is completed and we are sure most of the pieces are missing."
"These latest findings from the Mars Global Surveyor tell us that more study both from orbit and at the surface is needed to decipher the tantalizing history of water on Mars," said Dr. Jim Garvin, Mars Exploration Program Scientist at NASA Headquarters. "Our scientific strategy of following the water by seeking, conducting in situ studies, and ultimately sampling will follow up on these latest discoveries about Mars, and adapt to the new understanding."
"Mars seems to continually amaze us with unexpected discoveries," said Dr. Edward Weiler, Associate Administrator for Space Science at NASA Headquarters. "This finding just might be the key to solving some of the biggest mysteries on Mars, and it also tells us that our new Mars exploration program needs the flexibility to follow up in a carefully thought-out manner."
"The finding of layered sedimentary deposits is something that biologists have been hoping for," said Dr. Ken Nealson, director of the Center for Life Detection at NASA's Jet Propulsion Laboratory (JPL), Pasadena, CA. "Perhaps the favorite sites for biologists to search for fossils or evidence of past life on Earth are layered lake or oceanic sediments such as in these sites Malin and Edgett describe."
Images for this release are available at:
Information on the Mars Global Surveyor is available at:
NASA Press Release, 7/27/00
In 2003, NASA plans to launch a relative of the now-famous 1997 Mars Pathfinder rover. Using drop, bounce, and roll technology, this larger cousin is expected to reach the surface of the Red Planet in January, 2004 and begin the longest journey of scientific exploration ever undertaken across the surface of that alien world.
Dr. Edward Weiler, Associate Administrator, Office of Space Science, NASA Headquarters, Washington, DC., announced today that the Mars Rover was his choice from two mission options which had been under study since March.
"Today I am announcing that we have selected the Mars Exploration Program Rover rather than the orbiter option, which was an extremely difficult decision to make," said Weiler. "At the same time, we want to look into what could be an amazing opportunity, as well as a challenge, by sending two such rovers to two very different locations on Mars in 2003 rather than just one."
"We are evaluating the implications of a two-rover option, Weiler added. "I intend to make a decision in the next few weeks so that, if the decision is to proceed with two rovers, we can meet the development schedule for a 2003 launch."
With far greater mobility and scientific capability than the 1997 Mars Pathfinder Sojourner rover, this new robotic explorer will be able to trek up to 110 yards (100 meters) across the surface each Martian day, which is 24 hrs. 37 min. The Mars rover will carry a sophisticated set of instruments that will allow it to search for evidence of liquid water that may have been present in the planet's past, as well as study the geologic building blocks on the surface.
"This mission will give us the first ever robot field geologist on Mars. It not only has the potential for breakthrough scientific discoveries, but also gives us necessary experience in full-scale surface science operations which will benefit all future missions," said Scott Hubbard, Mars Program Director at NASA Headquarters. "A landed mission in 2003 also allows us to take advantage of a very favorable alignment between Earth and Mars."
After launch on top a Delta II rocket, and a cruise of seven and a half months, the spacecraft should enter the Martian atmosphere January 20, 2004. In a landing similar to that of the Pathfinder spacecraft, a parachute will deploy to slow the spacecraft down, and airbags will inflate to cushion the landing. Upon reaching the surface the spacecraft will bounce about a dozen times and could roll as far as a half-mile (about one kilometer). When it comes to a stop, the airbags will deflate and retract, and the petals will open, bringing the lander to an upright position and revealing the rover.
Where the Pathfinder mission consisted of a lander, with science instruments and camera, as well as the small Sojourner rover, the Mars 2003 mission features a design that is dramatically different. This new spacecraft will consist entirely of the large, long-range rover, which comes to the surface inside a Pathfinder landing system, making it essentially a mobile scientific lander.
Immediately after touchdown, the rover is expected to give us a virtual tour of the landing site by sending back a high resolution 360-degree, panoramic, color and infrared image. It will then leave the petal structure behind, driving off as scientists command the vehicle to go to rock and soil targets of interest.
This rover will be able to travel almost as far in one Martian day as the Sojourner rover did over its entire lifetime. Rocks and soils will be analyzed with a set of five instruments. A special tool called the "RAT," or Rock Abrasion Tool, will also be used to expose fresh rock surfaces for study.
The rover will weigh about 300 pounds (nearly 150 kilograms) and has a range of up to about 110 yards (100 meters) per sol, or Martian day. Surface operations will last for at least 90 sols, extending to late April 2004, but could continue longer, depending on the health of the rover.
"By studying a diverse array of martian materials, including the interiors of rocks, the instruments aboard the Rover will reveal the secrets of past martian environments, possibly providing new perspectives on where to focus the quest for signs of past life," said Dr. Jim Garvin, NASA Mars Program Scientist at NASA Headquarters. "Furthermore, the Rover offers never-before-possible opportunities for discoveries about the martian surface at scales ranging from microscopic to that of gigantic boulders. This is a key stepping stone to the future of our Mars exploration program."
One aspect of the Mars Rover's mission is to determine history of climate and water at a site or sites on Mars where conditions may once have been warmer and wetter and thus potentially favorable to life as we know it here on Earth.
The exact landing site has not yet been chosen, but is likely to be a location such as a former lakebed or channel deposit - a place where scientists believe there was once water. A site will be selected on the basis of intensive study of orbital data collected by the Mars Global Surveyor spacecraft, as well as the Mars 2001 orbiter, and other missions.
The alternative mission, which had been under consideration for the 2003 opportunity, was a Mars scientific orbiter, which featured a camera capable of imaging objects as small as about two feet (60 cm) across, an imaging spectrometer designed to search for mineralogical evidence of the role of ancient water in martian history, and other science objectives.
NASA Press Release
In what could turn out to be a landmark discovery in the history of Mars exploration, imaging scientists using data from NASA's Mars Global Surveyor spacecraft have observed features that suggest there may be current sources of liquid water at or near the surface of the red planet.
The new images show the smallest features ever observed from martian orbit -- the size of an SUV. NASA scientists compare the features to those left by flash floods on Earth.
"We see features that look like gullies formed by flowing water and the deposits of soil and rocks transported by these flows. The features appear to be so young that they might be forming today. We think we are seeing evidence of a ground water supply, similar to an aquifer," said Dr. Michael Malin, principal investigator for the Mars Orbiter Camera on the Mars Global Surveyor spacecraft at Malin Space Science Systems (MSSS), San Diego, CA. "These are new landforms that have never been seen before on Mars."
The findings were published in the June 30, 2000, issue of Science magazine.
"Twenty-eight years ago the Mariner 9 spacecraft found evidence -- in the form of channels and valleys -- that billions of years ago the planet had water flowing across its surface," said Dr. Ken Edgett, staff scientist at MSSS and co-author of the paper in Science. "Ever since that time, Mars science has focused on the question, 'Where did the water go?' The new pictures from Global Surveyor tell us part of the answer -- some of that water went under ground, and quite possibly it's still there."
"For two decades scientists have debated whether liquid water might have existed on the surface of Mars just a few billion years ago," said Dr. Ed Weiler, Associate Administrator for Space Science, NASA Headquarters. "With today's discovery, we're no longer talking about a distant time. The debate has moved to present-day Mars. The presence of liquid water on Mars has profound implications for the question of life not only in the past, but perhaps even today. If life ever did develop there, and if it survives to the present time, then these landforms would be great places to look."
The gullies observed in the images are on cliffs -- usually in crater or valley walls -- and are made up of a deep channel with a collapsed region at its upper end (an "alcove") and at the other end an area of accumulated debris (an "apron") that appears to have been transported down the slope. Relative to the rest of the martian surface, the gullies appear to be extremely young, meaning they may have formed in the recent past.
"They could be a few million years old, but we cannot rule out that some of them are so recent as to have formed yesterday," Malin said.
Because the atmospheric pressure at the surface of Mars is about 100 times less than it is at sea level on Earth, liquid water would immediately begin to boil when exposed at the martian surface. Investigators believe that this boiling would be violent and explosive. So how can these gullies form? Malin explained that the process must involve repeated outbursts of water and debris, similar to flash floods on Earth.
"We've come up with a model to explain these features and why the water would flow down the gullies instead of just boiling off the surface. When water evaporates it cools the ground -- that would cause the water behind the initial seepage site to freeze. This would result in pressure building up behind an 'ice dam.' Ultimately, the dam would break and send a flood down the gully," said Edgett.
The occurrence of gullies is quite rare: only a few hundred locations have been seen in the many tens of thousands of places surveyed by the orbiter camera. Most are in the martian southern hemisphere, but a few are in the north.
"What is odd about these gullies is that they occur where you might not expect them -- in some of the coldest places on the planet," Malin indicated. "Nearly all occur between latitudes 30 degrees and 70 degrees, and usually on slopes that get the least amount of sunlight during each martian day."
If these gullies were on Earth they would be at latitudes roughly between New Orleans, Louisiana, and Point Barrow, Alaska, in the northern hemisphere; and Sydney, Australia, to much of the Antarctic coast in the south.
The water supply is believed to be about 100 to 400 meters (300 to 1300 feet) below the surface, and limited to specific regions across the planet. Each flow that came down each gully may have had a volume of water of, roughly, 2500 cubic meters (about 90,000 cubic feet) -- about enough water to sustain 100 average households for a month or fill seven community-sized swimming pools. The process that starts the water flowing remains a mystery, but the team believes it is not the result of volcanic heating.
"I think one of the most interesting and significant aspects of this discovery is what it could mean if human explorers ever go to Mars," said Malin. "If water is available in substantial volumes in areas other than the poles, it would make it easier for human crews to access and use it -- for drinking, to create breathable air, and to extract oxygen and hydrogen for rocket fuel or to be stored for use in portable energy sources."
"This latest discovery by the Mars Global Surveyor is a true 'watershed'--that is, a revolution that pushes the history of water on Mars into the present," said Dr. Jim Garvin, Mars Program Scientist, NASA Headquarters. "To follow up on this discovery we will continue the search with Mars Global Surveyor and its rich array of remote sensing instruments, and in 2001, NASA will launch a scientific orbiter with a high spatial resolution middle- infrared imaging system that will examine the seepage sites in search of evidence of water-related minerals.
"Furthermore, NASA is in the process of evaluating two options for a 2003 mission to Mars, both of which could provide independent information concerning the remarkable sites identified by Malin and Edgett."
The Japanese Nozomi probe to Mars won't get to Mars until the end of 2003
or the beginning of 2004. A swing-by of the Earth, meant to take it out of Earth
orbit, failed in early 1999, and now Nozomi must orbit the sun three times before
trying another swing-by. Once at Mars, Nozomi will be in orbit for two years
to analyze Mars's atmosphere.
[based on information from Nature, 21 January 1999, 397, p. 193]
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