In addition to the 23 (!) Cameras on board the Mars2020 mission and the
small Ingenuity helicopter, Perseverance is carrying eight scientific
instruments and enough to take soil samples. A real laboratory to
discover in detail the Jezero crater!
To discuss the scientific
aspect of this mission, we spoke with teacher-researcher Erwin Dehouck,
from the Lyon Geology Laboratory (Earth, Planets, Environment), who
works daily with data from the Curiosity rover, and soon to
Perseverance.
On the team side, a lot of enthusiasm!
“It's a fantastic
opportunity”, explains Erwin Dehouck. Part of the scientific team
working today with the Curiosity rover will be in charge of the first
operations with its cousin, Perseverance. “There is an obvious
continuity between the two missions, at the technical level as well as
at the human level. We will discover a new place on Mars, and we will
help choose the first Martian samples that will return to Earth! At the
same time, it's also a challenge: as Curiosity continues to function
well, many of us are going to have to 'juggle' between the two projects
”.
However in France as in the United States, the whole team is
in the excitement of the departure… And this even if the rovers are
piloted from the JPL in California (Pasadena), which implies to work in
the evening, even until 2:00 am, Toulouse time!
NASA already organizes regular training sessions, so that all concerned
are ready by next February. 'I am a teacher-researcher, so I share my
time between teaching at the university and scientific research,'
explains Dehouck. My role will be quite similar, with Perseverance, to
what it is today with Curiosity: I will participate in the planning of
the rover's activities on Mars (which we call 'operations') in
particular with the SuperCam instrument, but also to scientific
discussions on data ”.
However, with a different organization,
details the planetologist, because the American agency has decided to
reduce the time between the moment when the data of the past day will be
received on Earth, and that or a new list of orders will be transmitted
to Mars. While perfect for optimizing the rover's activities, this will
require even greater interaction between colleagues!
Having two
missions such as Curiosity and Perseverance active at the same time is a
chance. Eight years apart, the two robots have a lot in common. “But
there are some analyzes possible with Curiosity that won't be possible
with Perseverance, and vice versa. Importantly, the two missions are on
two different sites. It would not occur to an Egyptologist to study only
one piece in a pyramid, and to abandon all the others. On Mars, it's a
bit the same thing: we need to have an overview of the planet in order
to accurately reconstruct its geological and climatic evolution,
”explains Erwin Dehouck.
What tools for Perseverance?
NASA has set itself four very
long-term objectives for the planet Mars: to determine whether life has
existed there, to precisely characterize its climate and geology, and to
prepare for future human exploration missions. We have to admit that
the instruments on board Perseverance correspond very well to these
objectives! On the body of the rover first, there is a very interesting
ground-penetrating radar at the rear, named RIMFAX (delivered by Norway)
and an experimental MOXIE box which will test the production of oxygen
and methane from atmospheric CO2. This is a very first test of the
so-called 'ISRU' technology for In-Situ Resource Utilization, that is to
say the production of useful resources for a future inhabited adventure
with the elements in place.
Placed both on the body and on the
Perseverance mast, we find the Spanish MEDA experience, which consists
in a way of a 'weather station' and measures wind speed, atmospheric
pressure, temperature, humidity and solar radiation. Also on the mast,
just under the “head” of the rover are the two Mastcam-Z stereoscopic
cameras, capable of zooming and capturing native color images of the
planet Mars, in 2D and 3D.
Perseverance also has, like its predecessor, a robotic arm 2 meters
long, at the end of which there is a scientific 'toolbox' with the PIXL
X-ray spectrometer and the SHERLOCK instrument which will attempt to
determine the nature of the minerals with very high resolution.
Above
all, we will also find the rotary drill of the rover, more impressive
than that of Curiosity. It should be able to take several grams of
material, then delicately deposit them in one of the 43 tubes carried by
the mission in front of the “caching system”. This device alone
represents an almost independent robot that operates in and under the
Perseverance sill. It collects, stores, sorts, seals the soil samples,
with its own robotic arm that remains inside the rover.
France is on board!
The big white case, the 'head of the rover'
which culminates at almost 2 meters high, is SuperCam, a multiple
instrument that brings French expertise into play. There is a laser
capable of pulverizing the rock to study it with the LIBS (Laser Induced
Breakdown Spectroscopy) technique and Raman spectrometry, a microphone
capable of listening to impacts (but also the mechanical noises of
Perseverance), a camera high resolution color for the background, and a
passive visible-infrared spectrometer (VISIR) which will analyze the
light reflected from the ground of Mars. It should be noted that the box
is only the visible facade of SuperCam, whose analysis instruments are
located inside the rover and connected by optical fiber.
“Supercam takes over the functionality of ChemCam, which uses an
infrared laser to remotely measure the chemical composition of rocks,”
confirms Erwin Dehouck. But he adds several more! The mission of
infrared and Raman techniques is to identify the minerals that make up
the rock, and possibly the organic molecules it contains. In other
words, in addition to the amount of the different chemical elements
present, we will now be able to know how these elements are assembled
with each other, which is crucial to understand the conditions under
which the rock was formed, if it encountered 'a lot of liquid water
since its formation, etc. '.
The teams will be able to take
advantage of the experience acquired with ChemCam to be more quickly
operational and efficient on Mars with the use of the new instrument.
No SAM on Perseverance ...
Finally, you may remember that France
and its laboratories contributed to the Curiosity mission with the SAM
instrument, which analyzes the samples dug by the rover's arm. A system
that has not been retained for Perseverance, which will leave its tubes
behind to be brought back to Earth. A disappointment for French
scientists?
“I imagine my colleagues on the SAM team would have
liked to have had a second copy on Mars! But this is not really the
philosophy of this mission, and there are two elements to remember, says
Erwin Dehouck. First of all, the work with Curiosity is far from over:
the teams are just about to collect a new sample for SAM! And above all,
there will be the mission of the European rover Rosalind Franklin with
its MOMA instrument, which will carry out certain analyzes similar to
those of SAM on the soil of Mars ”. However, it will be necessary to
wait until 2023 for the latter ...
Searching for 'traces of life', a scientific challenge
If all
goes well on takeoff this Thursday, July 30 and the arrival of the rover
on Mars on February 18 (and between the two), Perseverance will be able
to begin its exploration of the Jezero site, chosen after several years
of study, according to proposals from a scientific consortium. However,
for the public, it is not always easy to understand why Jezero (which,
on the visible level, will be just as deserted as the other Martian
places visited before him) is of major interest.
After all,
Curiosity also evolves within a crater (Gale) and there was a great deal
of evidence found there for the presence of water… “It's true, like
Gale, Jezero is an impact crater, but his diameter is about three times
smaller. Like Gale, the interior of Jezero was occupied by a lake at one
time - this can be seen by the very beautiful delta in its western part
(near which Perseverance will land), which resembles those found in the
mouths of rivers on Earth. One of the differences between the two sites
is that Jezero has an outlet, that is, a valley through which water
could exit the crater, while Gale was a hydrological 'terminus'. Another
important difference is the presence of areas rich in carbonates in
Jezero: these minerals are very common on Earth, but rare on Mars
(Curiosity found only a few traces in Gale); However, carbonates are
good indicators of past environmental conditions, and can preserve
possible biosignatures. These areas are priority targets for
Perseverance ”, explains Erwin Dehouck.
The planet Mars is often
described as being 'frozen in the past', because the conditions on its
surface have changed very little since it deserted more than 3 billion
years ago. In a way, it is an extraordinary chance to be able to observe
this preserved environment (the Earth having a geology and a much more
active climate, the primary conditions on its surface are long gone).
But we do not necessarily realize the difficulty in finding traces of
life. “The period in the history of Mars during which we believe that
its surface environment may have been 'habitable', that is to say
conducive to the emergence and development of life, is at a time when ,
on Earth, there were only single-celled and microscopic organisms. We
are therefore not looking for fossilized skeletons on Mars, ”Erwin
Dehouck recalls.
The answer lies in chemistry and geology. It is
therefore rather a matter of looking for elements which, by being
together one day, could allow the emergence of conditions favorable to
the development of life.
“These are much more discreet markers,”
says the planetologist. This can be mineral structures that cannot be
explained by purely abiotic processes, or even anomalies in the
abundance of certain organic molecules. Highlighting such markers, and
demonstrating that they are indeed linked to life, requires very
in-depth analyzes, which are difficult to carry out with a rover. Hence
the idea of bringing Martian samples to Earth! '.
We therefore
understand that it is not easy to find a consensus on the results of the
sensors sent to Mars, because what they observe is more akin to a
treasure hunt, to a bundle of presumptions that we then shapes with our
earthly knowledge of the living.
A treasure hunt that should not
leave room for speculation, so the return of samples should allow very
thorough analyzes, over long periods, by laboratories at the forefront
of research throughout the world. The advantage of a platform such as
Perseverance is that it is designed to travel several tens of
kilometers, and that it is sent to an area rich for its geological
diversity.
If all goes well, researchers may have an impressive
variety of soil samples from Mars within a decade. And when we know that
only a few grains of matter can reveal a lot about the past of the
planets, we better understand the impatience for the upcoming Mars
Sample Return mission!
This orientation for future collection and study is reflected in the
very conception of Perseverance's mission. “The rover is indeed very
well equipped for in situ analyzes, but the 'philosophy' of its payload
is different from that of Curiosity. Where the latter was designed as an
autonomous laboratory (hence the name of the mission: Mars Science
Laboratory), capable of carrying out long and complex analyzes on site
(X-ray diffraction, gas chromatography), Perseverance s' part of the
perspective of returning samples: like a field geologist, his priority
will not be to immediately resolve all the major questions that we ask
ourselves, but rather to identify, document and take the best rock
samples to be able to answer these questions after more in-depth
analyzes on Earth. That said, even if the samples were never to return,
we will learn a lot about Jezero and Mars thanks to the data from
Perseverance, ”concludes Erwin Dehouck.
Now, we must cross our
fingers for the landing of Perseverance on February 18, and hope that
the rover can deploy all its capabilities on Mars for a successful
mission, both now and in the long term!
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