Life as we know it can’t survive in the brine reported this week to flow intermittently on the Martian surface. But there may be other forms of life, which science hasn’t yet identified, that could thrive in that salty liquid or other potentially fertile zones of our solar system. So speculated several prominent scientists at a congressional hearing Tuesday about progress in the search for extraterrestrial life.
NASA’s chief scientist Ellen Stofan, speaking at a 29 September hearing of the House of Representatives’ Committee on Science, Space, and Technology, noted that the recently confirmed briny water contains a lot of perchlorate, a chemical commonly used in rocket fuel. “Based on what scientists know about life on Earth, that would not be a very habitable type of water,” she said. Stofan suggested, however, that our knowledge about where life can survive might be limited.
The new recognition that briny water flows occasionally on Mars came from fresh observations by NASA’s Mars Reconnaissance Orbiter (MRO) of dark streaks that were first seen to come and go on the planet’s surface in 2010. The day prior to the hearing, Mars investigators reported new spectrometer readings from MRO indicating the presence of hydrated salts associated with the streaks, confirming the involvement of liquid water in those features.
At the hearing, Stofan said that knowing there is near-surface water on the planet means that “maybe there could still be life forms on Mars today, deep underground, several meters below ground where the cosmic radiation that affects Mars would not affect them.” Scientists are encouraged that Mars “is the place where life maybe could have evolved” because liquid water was present long enough for chemical reactions to occur, she added.
“If I talk about the possibility of looking for exotic biochemistries on [Saturn’s moon] Titan, I’d better not say that life isn’t possible in the perchlorate solutions on Mars,” Jonathan Lunine, director of Cornell University’s Center for Astrophysics and Planetary Science, added at the hearing. He noted that it would be much easier to imagine the biochemistry on Mars than on Titan. In the Mars brine, “terrestrial life as we know it—bacteria, etc.—would all be sterilized by that solution. But is there a form of life that has evolved to live in that solution? That would be very interesting, but not impossible,” he said.
Looking Far and Wide
The new Mars findings came up during testimony about progress in the broader field of astrobiology, the study of life beyond Earth.
In the last 2 decades, Lunine said, scientists have made major strides identifying solar system locations that might harbor life or may have done so in the past. Lunine listed four of what he labeled “suspects,” which are Mars, Jupiter’s moon Europa, and Saturn’s moons Enceladus and Titan. He added that future planetary missions need smaller, lighter instruments to detect chemical signs of life and biological activity.
Other panelists at the hearing focused on astrobiology efforts beyond our solar system. Newfound abilities to find and study planets outside of our own solar system, known as extrasolar planets, give humankind “a chance to do an experiment of how life arises on terrestrial planets in a variety of environments, ” said Jacob Bean, assistant professor of astronomy and astrophysics at the University of Chicago.
Stofan noted that an updated NASA plan to guide research and technology development in astrobiology, originally due in 2014, would be issued later this year. “The reason it took longer is because this science is evolving so rapidly,” she said.
—Randy Showstack, Staff Writer
Citation: Showstack, R. (2015), Astrobiology hearing ranges beyond life as we know it, Eos, 96, doi:10.1029/2015EO036879. Published on 5 October 2015.