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Measure a Crater Yourself
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.
NASA has chosen two scientifically compelling landing sites for twin robotic rovers to explore on the surface of Mars early next year. The two sites are a giant crater that appears to have once held a lake, and a broad outcropping of a mineral that usually forms in the presence of liquid water.
Each Mars Exploration Rover (MER) will examine its landing site for geological evidence of past liquid water activity and past environmental conditions hospitable to life.
"Landing on Mars is very difficult, and it's harder on some parts of the planet than others," said Dr. Ed Weiler, NASA associate administrator for space science in Washington. "In choosing where to go, we need to balance science value with engineering safety considerations at the landing sites. The sites we have chosen provide such balance."
The first rover, scheduled for launch May 30, will be targeted to land at Gusev Crater, 15 degrees south of Mars' equator. The second, scheduled to launch June 25, will be targeted to land at Meridiani Planum, an area with deposits of an iron oxide mineral (gray hematite) about two degrees south of the equator and halfway around the planet from Gusev.
Which rover is targeted to a specific site is still considered tentative, while further analyses and simulations are conducted. NASA can change the order as late as approximately one month after the launch of the first rover. The first mission will parachute to an airbag-cushioned landing on Jan. 4, 2004, and the second on Jan. 25, 2004.
"A tremendous amount of effort has gone into evaluating possible landing sites in the past two years, to maximize the probability of mission success" said Peter Theisinger, MER project manager at NASA's Jet Propulsion Laboratory (JPL), Pasadena, Calif.
Images and measurements from two NASA spacecraft orbiting Mars provided scientists and engineers, evaluating potential landing sites, with details of candidate site topography, composition, rockiness and geological context.
"Meridiani and Gusev both show powerful evidence of past liquid water, but in very different ways," said Dr. Steve Squyres, principal investigator for the rovers' science toolkit and a geologist at Cornell University, Ithaca, N.Y. "Meridiani has a chemical signature of past water. Gray hematite is usually, but not always, produced in an environment where there is liquid water. At Gusev, you've got a big hole in the ground with a dry riverbed going right into it. There had to have been a lake in Gusev Crater at some point. They are fabulous sites, and they complement each other because they're so different," he said.
MER site selection began with identifying all areas on Mars that fit a set of engineering-driven requirements, said JPL's Dr. Matt Golombek, co-chair of a landing-site steering committee. To qualify, candidate sites had to be near the equator, low in elevation, not too steep, not too rocky and not too dusty, among other criteria; 155 potential sites were studied. A series of public meetings evaluated the merits of potential landing sites. More than 100 Mars scientists participated in the meetings.
"These two landing sites have been studied more than anywhere else on Mars. Both sites have specific scientific hypotheses that can be tested using the instruments on board each rover. It should be a very busy and exciting time after landing for the scientists analyzing the wealth of new data from the ground," said Dr. Cathy Weitz, MER program scientist at NASA Headquarters, Washington.
"Clearly there is tremendous interest in the science community in what these missions can accomplish and eagerness to help see that the rovers go to the best possible sites," said National Air and Space Museum's Dr. John Grant, the steering committee's other co-chair.
Once they reach their landing sites, each rover's prime mission will last at least 90 Martian days (92 Earth days). The rovers are solar-powered, and in approximately 90 days, dust accumulating on the solar arrays likely will be diminishing the power supply.
The twin MER spacecraft are at NASA's Kennedy Space Center, Fla., in preparation for launch. JPL manages the MER Project for NASA's Office of Space Science, Washington. JPL is a division of the California Institute of Technology in Pasadena.
Information about the MER project is available online here.
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/JPL imageScientists believe they've found an additional five meteorites that originated from the planet Mars. The new rocks were discovered during recent expeditions to Antarctica and the deserts of the Middle East and Africa--the best places for discovering the precious objects from space. This brings the total number of known Martian rocks to 24, and will provide researchers with additional specimens to analyze for evidence of past (or current) life on Mars. For more information, go to: http://www.jpl.nasa.gov/snc/news45.html
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
Mars Polar Lander
Mars Polar Lander who?
from the Prairie Home Companion Fifth Annual Joke Show submissions: Steven Gardner, Keyport, WA
If you would like to help mark and count craters in images from the Mars Global Surveyor, sign on to http://clickworkers.arc.nasa.gov/top. NASA's Ames Research Center is enlisting volunteers to look for possible craters on MGS and Viking images and click four places around each crater's rim. The volunteers are also asked to decide of the crater is fresh, degraded, or a "ghost." The project will help categorize craters of a smaller size than had previously been intensively studied.