Chapter 21:

Life in the Universe

ESA's Eddington Extrasolar-Planet Mission Axed

February 22, 2004

To save money, the European Space Agency's Eddington mission, which was to monitor stars to search for their surface oscillations and for exoplanet transits from the L2 Lagrangian point located between the Earth and the Sun, was cancelled in early 2004.

CETI Transmissions Made from Ukraine

July 7, 2003

A 70-m radio telescope in Evpatoriya, Ukraine, was used to broadcast messages toward 5 stars that are between 32-46 light-years away, starting on July 5, 2003.

http://www.teamencounter.com/missions/cosmic_call.asp

Extraterrrestrial Life Not Discovered with SETI@home

Planetary Society press release, March 26, 2003

Additional SETI@home information available on The Planetary Society's website at http://planetary.org/stellarcountdown/.

The SETI@home team has completed a successful run at the Arecibo radio telescope in Puerto Rico re-observing promising radio sources in the search for extraterrestrial intelligence. They collected data on 166 sources, exceeding their original goal of 150 candidates in this stellar countdown. Although the team discovered no evidence of a signal from an extraterrestrial civilization during a quick, real-time analysis of the data, they will take a more thorough look over the next several weeks.

The Planetary Society is the founding and principal sponsor of SETI@home, which is based at the University of California, Berkeley. SETI@home harnesses the computing power of four million volunteers to analyze data from the Arecibo telescope. Designed as an innovative screensaver program, SETI@home parcels out packets of raw data from Arecibo to be processed in the personal computers of volunteers around the world.

"The unique aspect of this project is that the public participates in real scientific analysis," said Bruce Betts, Director of Projects at The Planetary Society. "Millions of people around the world have helped get us to the point where we could identify potential targets and take a second look. Now the new data will go back to the SETI@home volunteers for more help with this early but critical step in our continuing search for extraterrestrial intelligence."

The final tally of sources observed during SETI@home's Stellar Countdown:

* SETI@home candidates -- 166
* extrasolar planetary systems (that might harbor earthlike planets) --5
* nearby sun like stars -- 35
* nearby galaxies -- 15
* candidates from Serendip SETI search -- 6

Seti@home's re-observations got underway on March 18 at Arecibo under the direction of Dan Werthimer, Chief Scientist of SETI@home. The initial run was interrupted by the need to use Arecibo's giant dish to observe a rare solar flare. On March 24 the team resumed observations and finished their run.

The candidates selected for re-observation were deemed the most interesting radio sources found out of the billions detected since the distributed computing project began to search for extraterrestrial intelligence in May 1999.

The Arecibo Observatory is a National Science Foundation facility that is part of the National Astronomy and Ionosphere Center, which is operated by Cornell University under a cooperative agreement with the NSF.

A Hot Jupiter Is Evaporating

Hubble European Space Agency press release, March 12, 2003

Using the Hubble Space Telescope, for the first time, astronomers have observed the atmosphere of an extrasolar planet evaporating off into space. Much of this planet may eventually disappear, leaving only a dense core. The planet is a type of extrasolar planet known as a "hot Jupiter". These giant, gaseous planets orbit their stars very closely, drawn to them like moths to a flame.

The scorched planet called HD 209458b orbits "only" 7 million kilometres from its yellow Sun-like star. By comparison, Jupiter, the closest gas giant in our Solar System, orbits 780 million kilometres from our Sun. The NASA/ESA Hubble Space telescope observations reveal a hot and puffed-up evaporating hydrogen atmosphere surrounding the planet. This huge envelope of hydrogen resembles a comet with a tail trailing behind the planet. The planet circles the parent star in a tight 3.5-day orbit. Earth also has an extended atmosphere of escaping hydrogen gas, but the loss rate is much lower.

A mainly European team led by Alfred Vidal-Madjar (Institut d'Astrophysique de Paris, CNRS, France) is reporting this discovery in the March 13 NATURE Magazine. "We were astonished to see that the hydrogen atmosphere of this planet extends over 200 000 kilometres," says Vidal-Madjar.

Studying extrasolar planets, especially if they are very close to their parent stars, is not very easy because the starlight is usually too blinding. The planet was also too close to the star for Hubble to photograph directly in this case. However, astronomers could observe the planet indirectly since it blocks light from a small part of the star during transits across the disk of the star, thereby dimming it slightly. Light passing through the atmosphere around the planet is scattered and acquires a signature from the atmosphere. In a similar way, the Sun's light is reddened as it passes obliquely through the Earth's atmosphere at sunset. Astronomers used Hubble's Space Telescope Imaging Spectrograph (STIS) to measure how much of the planet's atmosphere filters light from the star. They saw a startling drop in the star's hydrogen emission. A huge, puffed-up atmosphere can best explain this result.

What is causing the atmosphere to escape? The planet's outer atmosphere is extended and heated so much by the nearby star that it starts to escape the planet's gravity. Hydrogen boils off in the planet's upper atmosphere under the searing heat from the star. "The atmosphere is heated, the hydrogen escapes the planet's gravitational pull and is pushed away by the starlight, fanning out in a large tail behind the planet - like that of a comet," says Alain Lecavelier des Etangs working at the Institut d'Astrophysique de Paris, CNRS, France. Astronomers estimate the amount of hydrogen gas escaping HD 209458b to be at least 10 000 tonnes per second, but possibly much more. The planet may therefore already have lost quite a lot of its mass.

HD 209458b belongs to a type of extrasolar planet known as "hot Jupiters". These planets orbit precariously close to their stars. They are giant, gaseous planets that must have formed in the cold outer reaches of the star system and then spiralled into their close orbits.

This new discovery might help explain why "hot Jupiters" so often orbit a few million kilometres from their parent stars. They are not usually found much closer than 7 million kilometres, as is the case for HD 209458b. Currently, the current closest distance is 5.7 million kilometres. Hot Jupiters have orbits that are as brief as 3 days, but not shorter. Perhaps the evaporation of the atmosphere plays a role in setting an inner boundary for orbits of hot Jupiters.

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Notes

HD 209458b has a diameter 1.3 times that of Jupiter, and two-thirds the mass. Its orbit is one-eighth the size of Mercury's orbit around the Sun. The parent star is similar to our Sun and lies 150 light-years from Earth. It is visible with binoculars as a seventh magnitude star in the constellation of Pegasus. In 1999, this star suddenly entered the astronomical Hall of Fame when the extrasolar planet HD 209458b passed in front of it and partly eclipsed it. This was the first confirmed transiting extrasolar planet ever discovered. In 2001, Hubble detected the element sodium in the lower part of HD 209458b's atmosphere, the first signature of an atmosphere on any extrasolar planet.

The team is composed of A. Vidal-Madjar, lead author of the discovery, (Institut d'Astrophysique de Paris, CNRS, France) A. Lecavelier des Etangs, J.-M. Desert (Institut d'Astrophysique de Paris, CNRS, France), G. Ballester (University of Arizona, United States), R. Ferlet and G. Hebrard (Institut d'Astrophysique de Paris, France), and M. Mayor (Geneve Observatory, Switzerland). They observed three transits of the planet in front of the star with Hubble. The observations of the atomic hydrogen envelope were made in ultraviolet (Lyman-alpha) light, using Hubble's spectrograph STIS. Hubble's position above the atmosphere makes it the only telescope currently that can perform these types of ultraviolet studies.

The search and the study of extrasolar planets is the aim of several of ESA's scientific missions. Eddington, for instance, due for launch in 2007, will discover large numbers of transiting planets of all types, including many transiting 'hot Jupiters' similar to HD 209458b. These will be ideal targets for the same type of detailed follow-up studies with large space- and ground-based telescopes.

SETI@home Has 150 Candidates

Planetary Society press release, March 10, 2003

After nearly four years of searching for extraterrestrial intelligence, the SETI@home project will now take a closer look at its most promising candidate radio sources. The "Stellar Countdown" will use Puerto Rico's Arecibo radio telescope on March 18-20, 2003 to re-observe up to 150 of the most interesting radio sources found out of the billions detected since the distributed computing project began in May 1999.

David Anderson, SETI@home's Project Director, said, "After the re-observations of our Stellar Countdown help us eliminate candidates that are random noise or terrestrial radio interference, we will be very curious to see what candidates remain."

On-the-spot analysis of data during the Arecibo observing run will allow the team to re-target any especially promising signals. A more detailed analysis of the Stellar Countdown results will be conducted after the SETI@home team returns to UC Berkeley.

Candidate radio sources were chosen on the basis of several criteria:

- number of times the radio source was detected
- how closely different observations resemble each other
- strength of radio source
- proximity to known stars
- type of star (main sequence stars given preference)
- the presence of known planets

Dan Werthimer, Chief Scientist of SETI@home, will lead the team conducting re-observations at Arecibo. The researchers will observe the sky eight hours each day, staggering the time of day for each session to cover as much sky as possible.

Werthimer, who will head for the Arecibo observatory on March 16, said, "I believe that we will likely discover extraterrestrial civilizations in the next hundred years. Even if we don't find a signal from ET this time, I'm optimistic in the long run, since our search capabilities are doubling every year."

SETI@home is the largest computation in human history, logging a staggering 1.3 million years of computer time. The screensaver program runs on computers in homes, offices and schools worldwide, and volunteers range in age from school children to retirees.

"Whether or not SETI@home succeeds in finding evidence of extraterrestrial intelligence at this early date," said Bruce Murray, Chairman of the Society's Board of Directors, "this project has already made history. SETI@home has performed the most sensitive and detailed SETI sky survey to date, has demonstrated the power of the Internet for doing scientific distributed computing, and has allowed the general public to participate directly in an exciting research project."

The Planetary Society has provided privately raised funds for more than a dozen searches for ET around the world since 1983. Currently, it is supporting searches in both optical and radio frequencies.

Visit http://planetary.org/stellarcountdown to read daily updates from the Arecibo research team during the Stellar Countdown. The Planetary Society's website will also features maps of the candidate targets and articles about the re-observations, SETI@home, and the search for extraterrestrial intelligence. Dan Werthimer will be the guest on the Society's Planetary Radio program, Monday, March 17 (details on the website).

The Mars Meteorite Backers Don't Give Up

NASA RELEASE: 02-150, August 2, 2002

In the latest study of a 4.5 billion-year-old Martian meteorite, researchers have presented new evidence confirming that 25 percent of the magnetic material in the meteorite was produced by ancient bacteria on Mars. These latest results were published in the journal Applied and Environmental Microbiology.

The researchers used six physical properties they refer to as the Magnetite Assay for Biogenicity (MAB) to compare all the magnetic material found in the ancient meteorite -- using the MAB as a biosignature. A biosignature is a physical and/or chemical marker of life that does not occur through random processes or human intervention.

"No non-biologic magnetite population, whether produced by nature or in the laboratory, has ever met the MAB criteria," said Kathie Thomas-Keprta, an astrobiologist at NASA's Johnson Space Center (JSC) in Houston and the lead researcher on the study. "This means that one-quarter of the magnetite crystals embedded in the carbonates in Martian meteorite ALH84001 require the intervention of biology to explain their presence."

Magnetotactic bacteria, which occur in aquatic habitats on Earth, arrange magnetite crystals in chains within their cells to make compasses, which help the bacteria locate sources of food and energy. Magnetite (Fe3O4) is produced inorganically on Earth, but the magnetite crystals produced by magnetotactic bacteria are very different -- they are chemically pure and defect-free, with distinct sizes and shapes.

Four of the MAB biosignature properties relate to the external physical structure of the magnetite crystals, while another refers to their internal structure and another to their chemical composition.

In their earlier studies, the researchers found that approximately one-quarter of the nanometer-sized magnetite crystals in ALH84001 had remarkable physical and chemical similarities to magnetite particles produced by a bacteria strain on Earth called MV-1. This is the first time, however, that any researcher has used the full MAB range of biosignature properties to compare the proposed bacteria- produced crystals in Mars meteorite ALH84001with the bacteria-produced crystals from Earth and with the other magnetites in the meteorite.

The comparison between the proposed bacteria-produced crystals in the meteorite and crystals known to be produced by Earth-bacteria MV-1 is striking and provides strong evidence that these crystals were made by bacteria on Mars.

The fact that Mars Global Surveyor data suggest that early Mars had a magnetic field is consistent with a reason why Mars would have magnetotactic bacteria. "Our best working hypothesis is that early Mars supported the evolution of bacteria that share several traits with magnetotactic bacteria on Earth, most notably the MV-1 group," said Simon Clemett, a coauthor of the paper at Johnson.

Mars has long been understood to provide the sources of light and chemical energy sufficient to support life, but in 2001 the Mars Global Surveyor spacecraft observed magnetized stripes in the crust of Mars, which showed that a strong magnetic field existed in the planet's early history, about the same time as the carbonate containing the unique magnetites in ALH84001 was formed.

In June, researchers using the Mars Odyssey spacecraft announced that they had found water ice under the surface of Mars. These attributes, coupled with a carbon dioxide-rich atmosphere, would have provided the necessary environment for the evolution of microbes similar to the fossils found in ALH84001.

"We believe this latest study proves that the magnetites in ALH84001 can be best explained as the products of multiple biogenic and inorganic processes that operated on early Mars," Thomas-Keprta said.

An international team of nine researchers collaborated on the three-year study. The team, led by Thomas-Keprta of Lockheed Martin at Johnson Space Center, was funded by the NASA Astrobiology Institute. Co-authors of the study are Clemett and Susan Wentworth of Lockheed Martin at JSC; Dennis Bazylinski of Iowa State University (funded by the National Science Foundation); Joseph Kirschvink of the California Institute of Technology in Pasadena; David McKay and Everett Gibson of JSC; Hojatollah Vali of McGill University in Canada; and Christopher Romanek of the Savannah River Ecology Laboratory.

For a more technical discussion of this latest publication please visit the following Web site:

http://ares.jsc.nasa.gov/astrobiology/biomarkers/recentnews.html

Amino Acids Found in Interstellar Space

SETI Institute Press Release, March 27, 2002

Mountain View, CA -- A team of scientists including SETI Institute and NASA researchers today announced the successful creation of amino acids, chemicals essential to life, in a laboratory simulation of conditions found in deep space.

At NASA's Ames Research Center, Moffett Field, CA, the team reproduced the freezing conditions that exist in the gigantic interstellar clouds of dust, gas, and ice that are the birthplaces of new stars and planetary systems.

In their experiment, NASA scientists simulated space-like conditions by freezing mixtures of common molecules found in interstellar clouds then exposed them to ultraviolet radiation. When analyzed, the resulting material contained glycine, alanine, and serine, amino acids that play central roles in all living organisms on Earth. The team reported its results in the March 28 issue of the journal Nature.

"We had previously shown that the chemistry that occurs under these conditions makes a number of different types of organic compounds of biological interest," said Dr. Max Bernstein, first author and chemist at the Center for the Study of Life in the Universe at the SETI Institute and NASA Ames, "but because of their critical role in life on Earth, we really wanted to see if amino acids were in the mix."

"A variety of amino acids have previously been detected in certain kinds of primitive meteorites," noted Dr. George Cooper of Ames. "Their presence in meteorites proves that amino acids are, in fact, made in space. However, it has generally been thought that they were produced in the solar system within asteroids, the sources of most meteorites. Our latest work suggests that at least some of the amino acids found in meteorites may predate our solar system."

"Indeed," noted Dr. Scott Sandford of Ames, "these findings are particularly intriguing because the amino acids found in meteorites do show some signatures that suggest an interstellar connection. This connection, combined with our finding that amino acids can be made in interstellar clouds suggests that the Earth may have been seeded with amino acids from space in its earliest days."

"The infall of these materials on the early Earth may have facilitated the origin of life on our planet," said Dr. Jason Dworkin of the SETI Institute and Ames. "Furthermore, since new stars and planets are formed within the same clouds in which new amino acids are being created, this probably increases the odds that life has evolved elsewhere."

"It now seems possible that at least some of the amino acids found in meteorites predate the formation of our solar system and were in fact synthesized in interstellar space. If they were incorporated into meteorites, it's natural to ask if they would have been incorporated into comets as well. Since recent work [Amino acid survival in large cometary impacts (E. Pierazzo and C.F. Chyba). 1999. Meteoritics and Planetary Science 32, 909-918.] suggests that some amino acids should survive cometary impacts with Earth, there may be a direct link between prebiotic organic molecules on early Earth and interstellar space," says Dr. Christopher Chyba, a recent MacArthur Award winner who holds the Carl Sagan Chair and heads the Center for the Study of Life in the Universe (LITU) at the SETI Institute.

Previously, members of this team had demonstrated that irradiation of interstellar ice analogs results in the production of other compounds that are also of potential biological interest. These include a class of compounds called amphiphiles that can self-organize to form membranes and a class of compounds called quinones, aromatic ketones that play important roles in the metabolisms of living organisms on the modern Earth. "Taken in combination, these results suggest that interstellar chemistry may have played a significant part in supplying the Earth with some of the organic materials needed to get life started," Sandford concluded.

The mission of the SETI Institute is to explore, understand and explain the origin, nature, prevalence and distribution of life in the universe.

More detailed information about these findings can be found at:

http://astrochem.org

More information about the SETI Institute can be found at www.seti.org

Information about the Center for the Study of Life in the Universe can be found at
http://www.seti.org/science/litu/Welcome.html

Errata

In Box 2.1 on The Probability of Life in the Universe change the definition of f_i from "the fraction of these life forms that develop intelligence" to "the fraction of these life-bearing planets on which intelligence develops."