A new study has suggested optimal depths and locations to probe for organic molecules on Mars.
Stick a shovel in the ground and scoop. That’s about how deep scientists need to go in order to find evidence of ancient life on Mars, if there is any to be found, the study revealed.
Fortunately that’s within reach of Curiosity, the Mars Science Laboratory rover expected to land on the Red Planet next month.
The findings could help the newest Mars rover scout for evidence of life beneath the surface and within rocks.
The results suggested that, should Mars harbour simple organic molecules, NASA’s prospects for discovering them during Curiosity’s explorations are better than previously thought, said Alexander Pavlov of the NASA Goddard Space Flight Center in Greenbelt, Maryland, lead author of the study.
While these simple molecules could provide evidence of ancient Martian life, they could also stem from other sources like meteorites and volcanoes. Complex organic molecules could hint more strongly at the possibility of past life on the planet. These molecules, made up of 10 or more carbon atoms, could resemble known building blocks of life such as the amino acids that make up proteins.
Although complex carbon structures are trickier to find because they’re more vulnerable to cosmic radiation that continuously bombards and penetrates the surface of the Red Planet, the new research by Pavlov and his colleagues provides suggestions for where to start looking.
The amounts of radiation that rock and soil is exposed to over time, and how deep that radiation penetrates — an indicator of how deep a rover would have to sample to find intact organic molecules — is a subject of ongoing research.
The scientists report that chances of finding these molecules in the first 2 centimeters (0.8 inch) of Martian soil is close to zero. That top layer, they calculate, will absorb a total of 500 million grays of cosmic radiation over the course of one billion years — capable of destroying all organic material. A mere 50 grays, absorbed immediately or over time, would cause almost certain death to a human.
However, within 5 to 10 centimeters (2 to 4 inches) beneath the surface, the amount of radiation reduces tenfold, to 50 million grays. Although that’s still extreme, the team reports that simple organic molecules, such as a single formaldehyde molecule, could exist at this depth — and in some places, specifically young craters, the complex building blocks of life could remain as well.
“Right now the challenge is that past Martian landers haven’t seen any organic material whatsoever. We know that organic molecules have to be there but we can’t find any of them in the soil,” Pavlov said.
As Mars revolves around the Sun, it is constantly bombarded by very small meteors and interplanetary dust particles, which have plenty of organic compounds in them, Pavlov said. Therefore, over time they would have accumulated at the Martian surface.
Curiosity is the newest and largest of NASA’s Martian landers and is scheduled to touch down August 6 2012. Curiosity doesn’t have a shovel but, equipped with drilling technology, it will collect, store, and analyze samples of Martian material down to 5 centimeters below the surface of rock and soil.
Whether this 3.5-billion-year-old crater has fresher craters within it is uncertain. However, Pavlov hopes that his team’s findings will at least help guide NASA on where to drill once the rover has landed and influence where future generations of rover landers will touch down.
The study will be published 7 July in Geophysical Research Letters, a journal of the American Geophysical Union.