The EconomistJuly 25th 2020 Science & technology 632 goal is to measure the precise concentra-
tions in Mars’s atmosphere of substances,
including methane, water vapour, nitrogen
oxides and acetylene, that each form less
than 1% of the atmosphere’s total volume
but which might be signs of biology.
Methane is of particular interest since
its presence varies with both time and loca-
tion on the planet’s surface. Methane does
not live long in the Martian atmosphere,
suggesting there is an active source of the
gas. On Earth, living things emit methane
as they digest nutrients. But purely geolog-
ical processes can also liberate the stuff.
The next step in esa’s ExoMars pro-
gramme is a rover, called Rosalind Franklin.
This was also scheduled for launch in the
current window. However, a combination
of technical delays and the effect of co-
vid-19, which has meant the team of engi-
neers involved could not easily travel to
complete the manufacture and testing of
the rover, has pushed the lift-off date back
to the next favourable alignment, in 2022.
When Rosalind Franklineventually does
arrive on Mars (2023, if this timetable is ad-
hered to), the craft will crawl over an area
called Oxia Planum. This has clays that date
back around 4bn years, which will make it
the oldest site yet explored on Mars. Since
clay minerals require water to form, there
are high hopes that Oxia Planum may once
have been a life-friendly region.
Rosalind Franklin’s scientific payload
will be capable of much more sophisticated
analyses than Perseverance’s. In particular,
the Mars Organic Molecule Analyser
(moma) will be able to extract organic mol-
ecules from rocks and regolith more effec-
tively than before.
Previous attempts to study organic mol-
ecules on Mars have been plagued by the
presence of chemicals called perchlorates.
These were first seen in 2008, by nasa’s
Phoenixlander, and were confirmed by Cu-
riosityhalf a decade later. Those missions
baked their Martian samples in ovens, to
release the organics. That also released
chlorine and oxygen from the perchlorates,
and these oxidised most of the organic
molecules present. momawill circumvent
this problem by using an ultraviolet laser
that will knock organic molecules off rock
samples so fast that any perchlorates pre-
sent will not have time to decompose.
Rosalind Franklin’s most important tool,
however, will be a drill that can collect
samples from two metres below the sur-
face. This is crucial for recovering material
in which organic molecules can be found
in a good state of preservation. The thin
Martian atmosphere is easily penetrated by
ionising radiation from space. This slams
into the surface and even travels a little way
beneath it. As Jorge Vago, ExoMars’s lead
scientist, observes, “Over many millions of
years, this ionising radiation acts like ga-
zillion little knives slowly cutting away the
functionalgroupsoftheorganicmolecules
you would like to hopefully discover.” Use a
drill to go deep enough, though, and mate-
rial it collects will have been protected
from radiation by several metres of rock.
esa’s modelling suggests that samples
from 1.5 metres down would be scientifi-
cally interesting. The deepest any mission
has so far sampled under the surface of
Mars is a few centimetres.
The jackpot of this treasure hunt would
be to find things like sugars, phospholipids
(constituents of the membranes of cells),
nucleotides (the “letters” of genetic mate-
rial) or amino acids (the building blocks of
proteins) that are characteristic of life on
Earth. But consolation prizes might be
available in the form of less direct signals
of biology within the chemistry—traces of
the actions of enzymes, for example. As Dr
Vago observes, the way fatty acids are syn-
thesised biologically on Earth means that
they usually have an even number of car-
bon atoms, although there is nothing in
their underlying chemistry which favours
that in abiotic syntheses. Finding a pattern
like this, or something equally chemically
striking, in Martian organic molecules
would be encouraging to those who hope
that Mars has or once had life.Many hands
The uae’s launch of Al Amalshows how
even a small country can join the space race
if it is determined enough. No one, how-
ever, expects it to become a serious space
power. China, though, with half a dozen
visits to the Moon under its belt, already is
one. Nor is Tianwen-1the first Chinese at-
tempt to join the Mars club. In 2011 a craft
called Yinghuo-1 (“firefly”) attempted to
hitch a ride with Phobos-Grunt, a Russian
probe. Unfortunately, the rocket intendedto propel the combined mission on its way
malfunctioned, and it never left Earth or-
bit. This time, China is going it alone.
One thing which is known is that the
mission will host around a dozen scientific
instruments, including cameras, chemis-
try sets, magnetometers and radars. Offi-
cials from the China National Space Ad-
ministration say the plan is to make
detailed surveys of the surface. A ground-
penetrating radar, for example, will mea-
sure the thickness and composition of lay-
ers within the regolith and identify any ice
within 100 metres of the surface.
It will be a sophisticated spacecraft, if
details revealed about the landing system
are accurate. Zhang Rongqiao, the chief de-
signer, told Chinese television-viewers in
2019 that the lander would separate from
the craft’s main body at an altitude of 70
metres and hover until it found a safe land-
ing spot. Cameras and laser scanners will
help this lander avoid obstacles as it makes
its way to the surface.
Tianwen-1’s lander does not look capa-
ble, from its instrument list, of quite the
sorts of sophisticated biology-detecting
activity planned for Perseveranceand, after
it, Rosalind Franklin. But even if that is the
case, those other two vehicles, combined
with the forthcoming esa and nasa Mars
sample-return mission, do now offer a re-
alistic possibility of answering the ques-
tion of whether there is, or was, life any-
where other than on Earth. A failure to find
it would be a disappointment, although the
search would no doubt go on, both on Mars
and elsewhere. But an answer in the affir-
mative, even were that life only bacterial
and extinct, would surely transform hu-
manity’s view of itself as profoundly as did
the discoveries of Nicolaus Copernicus and
Charles Darwin. 7Stony ground or bountiful regolith?