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A Hitchhiker's Guide to Astrobiology

Looking for Microbial Martians

Space on Earth

In October, the sixth workshop of the European Astrobiology Network Association was held in Lyon, France. Scientists from around the world gathered to discuss topics such as interstellar chemistry, the origin of life, and the search for life in the solar system.

Martian Methane Ice

Looking at Life in Lyon


The city of Lyon, capital of France's Rhône-Alpes region, was founded by the Romans in the first century B.C. Now famous for its silk traders and puppeteers, Lyon has been a gathering point for Europeans for centuries. In October, Lyon hosted the sixth workshop of the European Astrobiology Network Association (EANA). Scientists from across Europe, as well as from places farther afield such as North America and China, gathered at the Ecole Normale Supérieure de Lyon to discuss topics such as interstellar chemistry, the origin of life, and the search for life in the solar system.

Modern stromatolites in Shark's Bay, Australia. Though rare today, such microbial communities represent some of the earliest life to develop on Earth.

Janet Siefert of Rice University in Houston, Texas discussed her study of the remnant of an ancient ocean in Mexico. This isolated lake is ringed by stromatolites, and provides in interesting modern analogue to the ancient stromatolites that are our earliest proof of life on the ancient Earth. Frances Westall of the Centre de Biophysique Moléculaire in Orleans, France discussed her studies of 3.5 billion-year-old stromatolites. She showed how even life this ancient was extremely sophisticated, and was therefore, in her view, "very far from the origin of life."

To try to understand how life did arise, many scientists focused on prebiotic chemistry, looking at what sort of elements were available for the early Earth. Because many of the elements are created in outer space and then spread across the universe, the conditions necessary for life's origin may literally be universal.

Once life got started on Earth, it had to struggle to sustain itself. Some of the presenters discussed strategies life devised in order to survive the harsh environment of Earth billions of years ago. For instance, Thierry Douki of the Commissariat à l'Énergie Atomique in Grenoble, France discussed how bacterial spores are highly resistant to UV radiation, and this perhaps indicates the level of extreme conditions of the early Earth. Andreja Zalar of the Institut National de la Recherche Agronomique in France pointed out that plant flavonoids found in seeds are even more UV-resistant than spores, and may represent an evolutionary leap in how organisms reproduced while still remaining protected from the sun's more damaging radiation.

Double vortex at Venus south pole. The Venus Express mission is starting to reveal new insights about our mysterious planetary neighbor.
Credit: ESA/VIRTIS/ INAF-IASF/Obs. de Paris-LESIA

From origins and early life on Earth, talks moved to investigations beyond our home planet. Christian Muller of the Belgian Institute for Space Aeronomy in Brussels provided some of the first results from ESA's Venus Express mission. Although they are still calibrating some of the instruments and the Planetary Fourier Spectrometer is currently not operational, mission scientists still have been able to make some observations about " Earth's Evil Twin." So far, no nitrogen molecules have been detected, which is considered bad news for astrobiology. Yet there are organic molecules in the clouds, and also some unidentified dark UV markings. Because Venus has no magnetic field, the solar wind whips the planet's atmosphere behind it as it orbits the sun, making Venus almost more like a comet than a planet. In fact, some have theorized that matter from Venus is transported to Earth by way of its "comet tail."

Bernard Foing of the International Lunar Exploration Working Group discussed the upcoming missions to the moon. China, India, Japan, the United States and Europe all have plans for lunar exploration in the next few years. Foing said the lunar rocks are completely devoid of organics, but there are hopes to locate polar ice and bring those samples back to Earth for analysis in the future.

Also discussed was the upcoming CoRoT mission, a space telescope that will search for extrasolar planets by looking for transits -- where a planet crosses in front of its star and therefore blocks some of the starlight that reaches us. CoRoT will be able to spot short period transits of 50 days or less, so only planets very close to their stars will be discovered by this mission.

CoRoT, due for launch in December 2006, will be the first spacecraft devoted to the search for rocky planets similar to our own Earth. It will look for the tiny drop in light caused by a planet as it slips across the face of its parent star.
Credits: CNES/D.Ducros

Another type of extrasolar detection is the search for biosignatures from other worlds, such as oxygen, ozone, carbon dioxide, methane, and water, or even a spectral signature that indicates photosynthetic bacteria or plant life. Our ability to read such spectral signatures is severely limited at present, but scientists are working on ways to improve our detecting techniques, or at least our ability to figure out exactly what we are detecting with current technology.

André Brack of the Centre National de la Recherche Scientifique in Orleans, France was one of the workshop organizers. Although this year's EANA workshop covered a broader range of topics than previous years, Brack said the presentations could be grouped into two major categories: primitive life on Earth as a reference for the search for life elsewhere, and studying pre-biotic chemistry to get at the question of how life arises in the first place.

"Life is organic chemistry in water, basically," said Brack. "We now know organic chemistry is universal, and we just have to look for biomarkers in places that have liquid water. So I would like to see more organic chemists involved in these kinds of studies."

Brack said he was heartened by the large numbers of young students attending the EANA workshop this year. That bodes well for the future of astrobiology in Europe, provided their interest can be sustained with available jobs. Like the United Sates, Europe has a deficit of students entering scientific fields. But at the same time, the general public has a great interest in science. Encouraging people to learn about and study astrobiology, which asks fundamental questions about the origin of life and the search for life elsewhere in the universe, could help bridge the gap between high public interest and the relative scarcity of those seeking scientific careers. Astrobiology workshops and conferences help bridge that gap by making the scientists talk in more general terms about the topics, thus providing tutorial lessons for people who merely have an interest or even are contemplating entering the field themselves.

The Miller-Urey experiment generated electric sparks -- meant to model lightning -- in a mixture of gases thought to resemble Earth's early atmosphere. Similar experiments have sought to solve the mystery of how life originated on the early Earth.
Credit: AccessExcellence.org

Brack said that astrobiology pioneers need to share their knowledge with the younger generation. Rather than being asked to reinvent everything, those just entering the field should know what has been worked on over the past 30 years. In addition, the workshop highlights the important questions that need to be addressed in the future. For Brack, one of the most important goals for astrobiology is to find evidence that life has arisen somewhere other than Earth.

"To be sure that life has a good chance of starting any time the necessary conditions are fulfilled, we need to find that second genesis," said Brack. "So far we have only one example of life, and so we cannot exclude the possibility that it was some kind of magic event which is non-reproducible. That would mean that life is restricted to the Earth, and is a real exception. In that case, we'd never be able to explain how it started, because we'd never be able to reproduce such a huge concordance of facts."

"But if we're convinced that life on Earth started when conditions were very typical, then life must be reproducible," he added. "Finding a second genesis would be wonderful proof that life is ubiquitous. If life does have a good chance to start anywhere, it must start very simple, and that means that we will be able, if we are patient enough, to explain and to reproduce something like life in the test tube. Then we will be able to give a plausible explanation for the start of life on Earth, and be confident that we'll find it in many other places in the universe."

By Leslie Mullen and Aaron Gronstal

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