Earth_Magazine_October_2017

instrument package offers an advantage over Curi-

osity’s organics analyzer, the SAM (Sample Analysis

at Mars) instrument suite, in that SHERLOC doesn’t

require contact with the sample, thus reducing

the chances of damaging or contaminating native

organic material.

Meanwhile, aboard the ExoMars rover will be an

instrument named MOMA (Mars Organic Molecule

Analyzer). MOMA can analyze powdered rock or

soil samples in two ways. With the first technique

— similar in concept to how SAM works — sam-

ples are oven-heated to separate volatile organics

from inorganics; the resulting gas is run through a

chromatograph and a mass spectrometer to separate

and identify different molecules. Using this method,

MOMA operators can also conduct chirality tests

on certain types of molecules to determine whether

they are “right-handed” or “left-handed” (the orien-

tation of biologically produced chiral molecules on

Earth), which could help distinguish biotic versus

abiotic origins.

The second MOMA technique uses a UV laser

to very rapidly heat samples and separate organic

materials, which are then analyzed in the mass spec-

trometer. This is designed to circumvent the problems

that Curiosity encountered with the perchlorate salts

abundant in Martian soils. When heated, perchlo-

rates become very powerful oxidants that can react

with and break down organic molecules into smaller

chlorinated compounds like chloromethane, Vago

says. This has complicated efforts to interpret the

organic materials Curiosity has detected, as the per-

chlorates alter the composition of the organics and

obscure information about their origins. “The beauty

of [MOMA’s] UV laser is that the deposition of energy

is so fast that the perchlorates don’t get enough time

to activate, so you can actually extract the organics

before [the perchlorates] mess them up,” Vago says.

Another ExoMars tool that may help in the search

for signs of past life is the rover’s drill. Whereas the

drills aboard NASA’s Curiosity and 2020 rovers pull

samples from the top several centimeters below the

surface, ExoMars’ drill is designed to reach down

as much as 2 meters underground. “We hope that

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