TheEconomistJuly 25th 2020 611A
round3.5bnyears ago conditions on
Earth and Mars were similar. Both had
thick atmospheres and liquid water on
their surfaces. Both, in other words, had
the conditions required to sustain life. And
on one of those planets life was, indeed,
sustained. Precisely when biology began
on Earth remains obscure. But by 3.5bn
years ago, a billion years after the solar sys-
tem formed, it was well established there
and has since evolved into the lush abun-
dance of complex forms seen today. Mars,
meanwhile, became a freezing desert.
The question nevertheless remains:
given that the conditions needed for life to
emerge on Earth also seem to have per-
tained for a time on Mars, might life have
evolved there, too? And, if it did, might it
still survive in some form, even if only in
vanishingly rare amounts?
To answer that question means visiting
the place—if not with people then at least
with robots. And now is a good time to do
so, for Earth and Mars are aligned in a way
that means the journey takes less than sev-
en months. On July 20th, therefore, the
first of a caravan of craft planning to take
advantage of this alignment set off. That
was when Al Amal, meaning “hope”, rose
from Japan’s spaceport on Tanegashima,
off the southern tip of Kyushu. Al Amalis an
orbiter intended to study Mars’s weather,
and also look at how the Martian atmo-
sphere is leaking into space. Its lift-off adds
the United Arab Emirates (uae) to the list of
countries that have dispatched probes to-
wards extraterrestrial bodies.
Al Amalwas followed, on July 23rd, by
Tianwen-1(“heavenly questions”), a Chi-
nese mission consisting of an orbiter, a
lander and a rover that took off from Wen-chang Space Launch Centre, on Hainan.
The lander’s provisional target is Utopia
Planitia, a large impact basin where an
American craft, Viking 2, touched down in- Chinese officials have so far declined
to release much detail about Tianwen-1’s
scientific aims, but what is known of them
suggests that it will study the distribution
of ice on Mars and examine how the plan-
et’s habitability has changed over time.
Lack of publicity has not been an issue
for the third member of the flotilla. On July
30th nasa, America’s space agency, hopes
to launch Perseverance, a one-tonne, six-
wheeled rover, from the country’s princi-
pal spaceport at Cape Canaveral, in Florida.
It will have cost $2.4bn to build and dis-
patch, and will absorb another $300m in
operating costs during its mission. It will
be the most sophisticated vehicle yet sent
by America to the Martian surface.
Once upon a time...
Perseveranceis aimed at a 45km-wide crater
called Jezero that was, 3.5bn years ago,
home to a lake. The rover’s main goal is to
look for signs of ancient life. But it is also
the opening gambit in a decade-long plan
to bring Martian rocks to Earth. Jezero itself
sits on the inner rim of Isidis Planitia, an-
other large impact basin, which was exca-
vated 3.9bn years ago. One source of the wa-
ter which formed the lake that once layAstrobiology
Life on Mars: the search continues
A new generation of biology-hunting spacecraft is on its way
Science & technology
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