Hunting martian fossils best bet for locating Mars life, researcher says

Feb 16, 2007
Mars in 2003, from the Hubble Space Telescope

Hunting for traces of life on Mars calls for two radically different strategies, says Arizona State University professor Jack Farmer. Of the two, he says, with today’s exploration technology we can most easily look for evidence for past life, preserved as fossil "biosignatures" in old rocks.

Farmer is a professor of geological sciences in ASU’s School of Earth and Space Exploration, where he heads the astrobiology program. He is reporting on his work today (Feb. 16) at the annual meeting of the American Association for the Advancement of Science in San Francisco.

"Searching for extraterrestrial life must follow two alternative pathways, each requiring a different approach and tools," Farmer says. "If we're looking for living organisms, we are doing exobiology. But if we are seeking traces — biosignatures — of ancient life, it’s better to call it exopaleontology."

Unfortunately, he notes, "for the next 10 or 15 years, technology limitations will force us down the exopaleontology path." The core issue is accessibility. "To find living organisms on Mars," says Farmer, "you need to find liquid water. Because liquid water is unstable on the Martian surface today, that means going deep into the subsurface."

Water saturates the ground in high latitudes north and south, and around both poles, only a few inches below the surface, Farmer explains. But this water remains frozen year round. "Environments with liquid water will likely lie far deeper, perhaps miles below the surface."

Organisms have been found living in fractured rock, thousands of feet underground on Earth, Farmer notes. "But with current robotic technology, we simply can’t drill that deep on Mars."

Terrestrial deep drilling requires complex, heavy equipment, plus constant supervision and troubleshooting by human crews. Says Farmer, "We’ll be lucky if, in the next decade or so, robotic drilling on Mars reaches a depth of a couple yards."

So where does that leave us in the search for life on Mars? Farmer says our best choice is to pursue the exopaleontology path.

"Finding the signatures of an ancient Martian biosphere means exploring old rocks that might preserve traces of life for millions or billions of years," Farmer notes. Among the best places to look on Mars, he says, are deposits left by springs and former lakes in the heavily cratered highlands. "The rocks there date from a period in Martian history when liquid water was common at the surface." In fact, says Farmer, conditions on Mars then were likely similar to those on the early Earth at the time when life began.

"Besides water, life also requires energy sources and organic chemical building blocks," Farmer explains. "The Mars Exploration Rover Opportunity found ample evidence for water in ancient rocks at Meridiani Planum, but the rovers’ instruments can’t detect organic materials." However, NASA’s next rover, the Mars Science Laboratory, will carry instruments to analyze traces of organic substances. It is due for launch in 2009.

Recognizing a Martian fossil may be difficult. "We’re not talking about stumbling over dinosaur bones," Farmer says.

Instead, the discovery may involve finding biologically formed structures in old sedimentary deposits, perhaps like stromatolites found here on Earth. Stromatolites are distinctive structures that form in shallow oceans, lakes, or streams where microbial colonies trap sediments to form thin repeating layers.

Stromatolites also contain microscopic cellular remains and chemical traces left by the microbes that formed them. Taken together, such structures comprise the primary record of life in ancient rocks on Earth.

For hunting Martian fossils, says Farmer, we will need robotic microscopic imagers capable of viewing rocks in many wavelengths as well as seeing details as small as a hundredth of a millimeter across. Also needed are organic chemistry laboratories to analyze promising rocks. "That will help us avoid mistaking non-biological features for biological ones," he says.

Farmer's fieldwork has taken him to extreme microbial habitats in Iceland, New Zealand, Yellowstone National Park, and Mono Lake, Calif. He has sought to understand how modern microbial communities become preserved as fossils. Their environments, he notes, span physical and chemical conditions believed to be representative of early Mars.

"Studying how microbes become fossils is a key step in developing an effective strategy for exopaleontology," Farmer says. "It will help us find the best places to explore on Mars and how to look."

Source: Arizona State University

Explore further: NASA's space station Robonaut finally getting legs

add to favorites email to friend print save as pdf

Related Stories

India reaches for Mars on prestige space mission

Nov 03, 2013

India began a countdown Sunday to the launch of its most ambitious and risky space mission to date, sending a probe to Mars which was conceived in just 15 months on a tiny budget.

From Sea2Sky: Inspiring science across Europe

Oct 19, 2012

On the last Friday of September people gathered across 800 venues in 320 cities located in 32 European countries to take part in European Researchers' Night - a free, day-long research festival dedicated ...

In search of virus fossils

Oct 19, 2011

Here's a theory for a comedian to consider: dinosaurs done-in by avian flu. Silly as that may be, we imagine that viruses have been infecting organisms since life first appeared on Earth, but this is mostly ...

NASA Instrument Will Identify Clues to Martian Past

Jun 28, 2010

(PhysOrg.com) -- NASA's Curiosity rover, coming together for a late 2011 launch to Mars, has a newly installed component: a key onboard X-ray instrument for helping the mission achieve its goals. Researchers ...

Recommended for you

NASA's space station Robonaut finally getting legs

10 hours ago

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Sun emits a mid-level solar flare

Apr 18, 2014

The sun emitted a mid-level solar flare, peaking at 9:03 a.m. EDT on April 18, 2014, and NASA's Solar Dynamics Observatory captured images of the event. Solar flares are powerful bursts of radiation. Harmful ...

Impact glass stores biodata for millions of years

Apr 18, 2014

(Phys.org) —Bits of plant life encapsulated in molten glass by asteroid and comet impacts millions of years ago give geologists information about climate and life forms on the ancient Earth. Scientists ...

The importance of plumes

Apr 18, 2014

The Hubble Space Telescope is famous for finding black holes. It can pick out thousands of galaxies in a patch of sky the size of a thumbprint. The most powerful space telescope ever built, the Hubble provided ...

User comments : 0

More news stories

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Cosmologists weigh cosmic filaments and voids

(Phys.org) —Cosmologists have established that much of the stuff of the universe is made of dark matter, a mysterious, invisible substance that can't be directly detected but which exerts a gravitational ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...

Airbnb rental site raises $450 mn

Online lodging listings website Airbnb inked a $450 million funding deal with investors led by TPG, a source close to the matter said Friday.