We want to know: has life ever existed on Mars?
Do pockets of life persist on Mars today?
NASA's approach to answering these questions is to break them
down into smaller and smaller steps.
First, we need to know if ancient Mars was habitable.
Did it once have the right climate, and the right chemistry
to support life?
The Curiosity rover is investigating these questions by
looking for organic molecules: containing carbon.
Organic molecules are the backbone of all life on Earth,
though they can also come from non-living sources.
Today the surface of Mars readily destroys organics,
making them difficult to detect.
Six years ago, Curiosity landed in Gale Crater, on an ancient
lakebed.
A few months after arrival, it drilled into sedimentary rocks
and detected traces of organic molecules using an instrument
called SAM.
Now, Curiosity is climbing the mound in the middle of Gale
Crater, and SAM has made a subsequent detection of
organics.
This new detection is exciting because it comes from rocks that
are billions of years old.
That means that the organic material within them is
extremely ancient.
Some of the organics that SAM has detected contain sulfur,
likely introduced through geological processes.
Sulfur can act as a preservative, binding organic
molecules together to make them tougher, and protecting them
from oxidation.
In fact, sulfur is the element that makes hair and fingernails
tough, as well as vulcanized rubber.
Martian sulfur has probably had a similar effect on these old
organic molecules, helping to preserve them over geological
timescales.
SAM made the new detections by heating samples of crushed rock
to very high temperatures, above a thousand degrees Fahrenheit.
This vaporized the samples and released several species of
small hydrocarbons, like benzene and propane.
Because the hydrocarbons were released at such high
temperatures, they may be the fragments of bigger, heavier
molecules within the rock similar to kerogens.
On Earth, kerogens are found in rocks like black shale and coal,
and are the products of ancient plant and bacteria.
We don't know if the recently discovered organics on Mars are
of biological origin, but it's exciting to find such old
material preserved right at the surface.
This finding is also encouraging for future exploration.
NASA and the European Space Agency are preparing to send the
next generation of rovers to Mars in 2020, carrying new
technologies to search for signs of microbial life.
In the distant past, Mars was much warmer and wetter than it
is today.
The rocks at Gale Crater tell us it was once an environment where
life as we know it could have survived.
The discovery of ancient organic molecules shows that another
ingredient of life was present at that time, and it broadens
our understanding of habitability of both ancient and
modern Mars.
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