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A Hitchhiker's Guide to Astrobiology

Looking for Microbial Martians

Space on Earth

Summary (May 29, 2006): In early May, scientists met in Stockholm, Sweden for the first Nordic Astrobiology conference. This overview provides a look at some of the conference presentations, which dealt with the origin and distribution of life in the universe.

Martian Methane Ice

The Nordic Invasion

Sunny Stockholm, the site of the first Nordic Astrobiology conference.
Photo by: Leslie Mullen

The Vikings are coming!

In early May, astrobiologists gathered in Sweden to sample smörgåsbord and to discuss planetary, space, and life sciences. While there is already an astrobiology network for Europeans - the European Astrobiology Network Association (EANA) - the shared culture and geography of Sweden, Finland, Norway, Iceland, and Denmark, and also the Baltic States and Russia, make a Nordic astrobiology community necessary as well.

"[Sweden] shares the geographic peripheral position with the other Nordic countries," said conference organizer Nils Holm, a professor of marine geochemistry at Stockholm University. "European maps that you buy in France, for example, normally don't include central and northern Sweden. You need to use so much paper if you want to include that part."

Holm said that astrobiology has been late coming to the Nordic countries, but now that their researchers are interested in pursuing it, they hope to get an increase in funding from the Nordic Council. Adding to this transition is the move of NORDITA - the Nordic Institute for Theoretical Physics - from Denmark to Sweden.

"We're in the build-up phase," said Holm. "Now that the NORDITA institute has moved from Copenhagen to Stockholm, we're hoping to see a transition from just pure graduate school education to something that's more research oriented."

Not all the presenters at the 2006 Nordic Astrobiology conference came from the North, however. Chris McKay of the NASA Ames Research Center in California started the conference off with a bang, giving a spirited public lecture about the evolution of Mars and the possibility that life could have evolved there. Later in the conference, McKay described his theory for what life might be like in places like Mars and Jupiter's moon Europa, and suggested search strategies to look for that life.

Chris McKay wonders if life could have evolved on Mars - and asks how we could find any evidence of it. Credit: Metro Publishing, Inc.

The problem of defining life was an issue tackled early on in the conference. Radu Popa of Portland State University said that astrobiology needs a numerical definition for life. Chemicals don't matter, he claimed, because they are just small parts of a larger trend toward organization. He argued that the origin of life occurred when information became digital - when it became encrypted, and required translation.

The basic requirements of life appear to be a metabolism, a template for making copies, and a membrane bag to hold it all together, said Eörs Szathmáry of Collegium Budapest. But how did such a complex system emerge from the primordial chemical soup? Enzymes speed up the chemical reactions life wants compared to other reactions that are not as favorable, he noted. But if you track the evolution of this system backwards, you lose the preferred reactions in the chemical reaction noise. This limitation makes it very difficult to trace life back to its origin.

Tracing life back to its original components is the focus of research by Pascale Ehrenfreund of Leiden University in the Netherlands. She discussed what sort of chemicals early life may have developed from, based on the raw materials provided by the solar system. 143 interstellar and circumstellar molecules have been detected in space, and among those, and also in meteorites, astronomers have found important molecules for life, including purines, sugars, amino acids, and fatty acids. Polycyclic aromatic hydrocarbons make up 10 to 20 percent of the cosmic carbon, said Ehrenfreund, and its durable molecular structure could have been important for life's origin.

Some of the ingredients for life are produced in the diamond-bright star fields of space. Credit: NASA/STScI/ESA

Moving on from life's beginning to the search for life elsewhere, many conference talks focused on exploration and conducting experiments in the field, in places ranging from extreme environments on Earth to the surface of the Moon. Some of the tools that scientists may be using in the near future were discussed, including the International Lunar Astrobiology Laboratory (ILAL). This instrument, under preliminary investigation by the European Space Agency and Alcatel Alenia Spazio, involves miniaturizing laboratory equipment to be used in astrobiology studies, creating the perfect astrobiologist's suitcase for travel to any remote location.

Of course, researchers don't have to travel into space to find extreme environments. Life on Earth exists in all kinds of amazing places, including far below the surface of our planet in rocks and sediments that are isolated from oxygen and sunlight. Scientists once thought that life could not be found deep below the ground, but as Karsten Pedersen of Sweden's Göteborg University explained, microbes can live hundreds of meters below the surface, and in the same abundance that we find in some surface ecosystems. Pedersen discussed the diversity of these unique microbes, the multitude of underground habitats they can live in, and the unique strategies that scientists must employ in order to study them - from drilling deep holes to exploring mine shafts.

Hans Rickman, of the Uppsala Astronomical Observatory in Sweden, led the final session of the conference by discussing how water and other volatiles may have been delivered to the Earth and other terrestrial planets in the early days of the solar system. These important components for the origin of life may have come from sources on the planet itself, or could have been delivered by asteroids and comets. Rickman emphasized this last point by detailing the transfer mechanisms that could have moved transneptunian comets, or comets that are near to or beyond the orbit of Neptune, toward the center of the solar system where they could collide with the young Earth.

Looking for signs of life deep underground, in a South African mine shaft.
Photo by: Louise Gubb

His research raises questions about the origin of the Earth's Moon as well. If the Moon was created by a large comet or asteroid impact, any water or volatiles on the planet would have been vaporized or lost. This means that water may have appeared on Earth after the massive Moon-forming impact.or maybe the impact itself was not as large as we previously thought.

Many of the conference presentations will be published as papers in the journal Astrobiology in the coming months. This first official meeting of the Nordic astrobiology group showed that, rather than pillage and plunder like the Vikings of old, Nordic astrobiologists hope to expand current astrobiology research efforts, and contribute to future exploration missions.