IMAGE: ESA/ATG MEDIALAB124 8 APRIL 2022 • VOL 376 ISSUE 6589 science.org SCIENCE
A
fter a technical review, the European
Space Agency (ESA) confirmed last
week that its Mars rover was ready
for launch. The only problem: The
rover has neither a ride to the Red
Planet nor a landing craft to get it
safely to the surface. Russia was supposed
to provide both, but ESA suspended ties and
canceled a planned launch in September
after the country invaded Ukraine. “There
was no real alternative,” says ExoMars team
leader Thierry Blancquaert of ESA’s tech-
nology center in the Netherlands.
Now, ESA is studying options to keep the
€1 billion mission alive. Even if the agency
can replace the Russian technologies—and
pay for them—a delay to 2028 or even 2030 is
likely, Blancquaert says. Planetary scientists
say the rover will be worth the wait. “The
mission will still be cutting edge even for
potentially later launch windows in the next
decade,” says Andrew Coates of University
College London, principal investigator of the
rover’s panoramic camera.
ExoMars has not had an easy gestation.
It was originally an ESA-NASA collabora-
tion, but the United States pulled out in 2012
for budgetary reasons. Russia stepped in to
provide a Proton rocket for its launch, and
a landing vehicle called Kazachok. Russian
scientists also provided most of the instru-
ments on Kazachok, which will form a sensor
station after landing. And Russia contributed
two of the nine instruments for the mis-
sion’s centerpiece: a rover the size of a golf
cart, named Rosalind Franklin after the Brit-
ish DNA pioneer. It can drill 2 meters below
the surface in search of pristine samples that
may yield evidence of past life.
The change in parentage caused the launch
date to slip from 2018 to 2020. (Launch op-
portunities for Mars occur roughly every
2 years when the planets align.) But in early
2020, difficulties with the parachutes de-
signed to slow descent into the martian at-
mosphere led to another 2-year delay.
This time around, “All the hardware
was ready to start the launch campaign,”
Blancquaert says. The rover and Kazachok
were ready to be shipped to Russia’s space-
port in Baikonur, Kazakhstan, when Russia
began its war with Ukraine. “As soon as we
saw this Iron Curtain descend again, we
thought: What can we do to save ExoMars?”
Blancquaert says.
ESA is embarking on a 3-month study
to assess what’s possible. If relations with
Russia are restored swiftly, a 2024 launch
is still possible, Blancquaert says, but, “If
we need to change hardware, there’s no way
we would be ready.” As the war drags on in
Ukraine, a quick rapprochement looks in-
creasingly unlikely.
In that case, ESA will have to replace sev-eral critical technologies. One is radioisotope
heating units (RHUs), small capsules of radio-
active plutonium-238 that keep the rover
warm during the frigid martian night. NASA
has provided RHUs in the past, and the
United Kingdom could develop some later
this decade, but there are no other European
providers. ESA has RHUs leftover from the
development of its Huygens Probe, which
dropped to the surface of Titan in 2005. But
because they put out less power than the
Russian ones, more would have to be packed
aboard, possibly leading to the ouster of an
instrument, Blancquaert says.
Another technology Russia was to pro-
vide is retrorockets, used to take over from
parachutes in the final stages of descent.
ESA tested some simple retrorockets in 2016
with its Schiaparelli lander, which crashed
in its final approach to Mars because of a
software error. “In Europe we have not yet
matured this technology,” Blancquaert says.
A 2026 launch date might be possible if
ESA had help. NASA has said it is in dis-
cussions with ESA to see what it could pro-
vide. “NASA doesn’t have a billion dollars
to build ESA a lander,” says aerospace en-
gineer Zachary Putnam of the University of
Illinois, Urbana-Champaign, who has stud-
ied Mars landing systems for NASA. But if
ESA was just looking for RHUs and retro-
r o c k e t s , U. S. s u p p l i e r s c o u l d p r o v i d e t h e m , h e
says. If ESA must go it alone, however, 2028
looks like the earliest possible launch date,
Blancquaert says: “It gives us more time to
finalize European technology.”
ESA is relatively comfortable with other
lander elements trialed by Schiaparelli, such
as the heat shield, parachutes, and naviga-
tion system. And the agency also has a ready
launch solution: its new Ariane 6 rocket,
which may fly before the end of this year.
But such rockets aren’t cheap, and adapt-
ing ExoMars for a new launcher will cost
money. Keeping the spacecraft fit to fly and
employing research teams during the delay
also add to the expense. When the launch of
NASA’s InSight Mars lander was delayed, it
cost the agency about $150 million per year
to keep it on ice, Putnam says. On top of
that, developing a new lander for ExoMars
“could run to as much money as the rover
itself,” he says.
Meanwhile, ESA is planning another rover
and an orbiter, due for launch in 2027, that
are part of a $7 billion joint effort with NASA
to bring martian rocks back to Earth. Exo-
Mars team members will be eyeing a No-
vember meeting of the ESA council, when
budgets are set and the troubled mission will
be weighed against other Mars plans. jEurope tries to save Mars rover
after split with Russia
Team leader says delay to 2028 or 2030 is likely
PLANETARY SCIENCE
A European rover was set to go to Mars with a Russian
landing platform—until the invasion of Ukraine.By Daniel Clery