Life On Mars? Perseverance found organic molecules!
It is one of our greatest cosmic misfortunes that we have
completely missed the golden age of Mars... About 3.5 billion years ago, during the first
billion years of the solar system's existence, the Red Planet was indeed a blue planet,
flooded with oceans, seas, and rivers as Earth is today. But all was lost--even before the same
great miracle began to take place on our planet. Ancient sedimentary basins, delta estuaries,
and river beds are all that remain of Mars' watery past, which ended when the planet's magnetic field
broke down, allowing the solar wind to drag away the atmosphere and water to be lost to space.
Many things could have happened in that first billion years, including the emergence of life.
On Earth, life began well before the planet's billionth birthday, leading many
exobiologists-scientists studying the possibility of extraterrestrial life to believe that wherever
there is liquid water and the correct chemistry, biology could quickly take hold.
We've believed it to such an extent that we've done nothing but send at least a
dozen robotic machines between landers and rovers into the sands of the red planet
over the past few decades, not counting those that didn't make it--just as many.
Remotely controlled explorers, stationary or self-propelled chemical laboratories--all
employed to provide an answer to the question that most torments our anxiety as creatures
who feel alone in a universe that at the moment seems to be made of matter alone.
And now, it is news these days, after years of faint signs and only partial clues,
it seems that our faith in a concept of life extended to all planetary environments may
be rewarded by a discovery made by the latest robotic explorer to land on Mars:
The Perseverance rover, in fact, reached an area of high geological interest this summer,
and initial analyses of the sedimentary rocks it collected confirm a wet past and the presence
of a high concentration of organic molecules compatible with the development of life forms.
Let's try to figure out together if this is something really important--but first,
let's take stock of the scenario that led to this situation, shall we?
Perseverance is a car-sized Mars rover designed to explore the Jezero crater on Mars.
It was manufactured by the Jet Propulsion Laboratory and launched on 30 July 2020.
Confirmation that the rover successfully landed on Mars was received on 18 February 2021.
Perseverance has a similar design to its predecessor rover, Curiosity,
although it was moderately upgraded. It carries seven primary payload instruments,
nineteen cameras, and two microphones. They also differ in important mission-specific ways:
while Curiosity has identified and continues to study environments where ancient microbes
could have lived, Perseverance will seek direct signs of ancient life and prepare
geological samples that a future mission could bring back to Earth.
The rover also carried the mini-helicopter Ingenuity to Mars, an experimental aircraft
that made the first powered flight on another planet on 19 April 2021.
The Perseverance rover has four main science objectives that support the
Mars Exploration Program's science goals:
Looking for habitability: identify past environments that were
capable of supporting microbial life. Seeking biosignatures: Seeking signs of
possible past microbial life in those habitable environments, particularly in specific rock types
known to preserve signs over time. Caching samples: collect core rock
and regolith ("soil") samples and store them on the Martian surface.
Preparing for humans: test oxygen production from the Martian atmosphere.
Perseverance's destination, the Jezero crater, was announced by NASA back in November 2018.
And the site was chosen from more than 60 possible candidates-which makes one realize
how extraordinary its characteristics must be The explanation for so much consideration lies in
the fact that Jezero represents from a geological and biological point of view, a real gold mine.
In its more than 45 kilometers of extension, the crater is in fact home to an ancient delta
formed a few years ago 3.5 billion years ago at the convergence of a Martian river and a lake.
To realize this, one only has to look at a satellite photo of it.
Even at a first glance, one can recognize rock formations that can be traced to the
delta-like mouths of three rivers: two tributaries and one outflow.
The sedimentary bed that makes up the delta was deposited in very remote ages when water flowed
over the Martian surface and the river flowed into the crater forming a lake. The waters flowing into
a lake carry fine material that, as the estuary opens and the velocity decreases, is deposited
in large quantities, forming stratifications. It is precisely this peculiarity that may have
preserved any organic material intact at depth. If life was present on Mars at the time,
then some trace may have remained preserved within the rocky layers,
protected from the atmospheric changes that slowly transformed the planet into its present state.
After spending its first year traversing the bottom of the ancient lake, however,
finding not sedimentary rock but compact igneous rock, probably formed by the fall
of the asteroid that excavated the crater, in April 2022 Perseverance
finally arrived in the delta region, where the second phase of its mission began.
Perseverance's mission to search for biomarkers on the Martian surface is in
fact divided into several campaigns named after each area of interest.
The Crater Floor Campaign, which began soon after arrival on the red planet in February 2021,
engaged the rover on the crater floor in search of the best rocks to sample.
Heading initially south from its landing point,
Perseverance then reached the sand dunes of Séítah from the east, then ascended north,
and finally took a final westward direction to reach the river delta.
And it was in that chaotic and very interesting region last July,
as NASA reports, that the rover collected the long-cherished evidence.
In fact, Perseverance took some samples from a rock formation called Wildcat Ridge--probably
formed when water slowly began to evaporate and mud and fine sand began to settle.
A couple of samples were taken from a rock outcrop known as Skinner Ridge,
which is made of fine-grained sandstone similar to a type of rock seen in many places on Earth.
Seen up close in the sampling tubes where Perseverance is storing the finds,
the Skinner Ridge cores appear light-colored and studded with round grains of dark material.
These darker grains were probably transported by the ancient river
that once flowed to Jezero from regions perhaps hundreds of kilometers away.
Thus, the study of the grains could tell scientists the story of distant areas of Mars.
The other pair of samples comes from a spot called Wildcat Ridge,
a sedimentary rock about a meter wide that is only 20 meters from Skinner Ridge. These
samples are lighter in color, more homogeneous, and finer-grained than the cores of Skinner Ridge.
And Earth's geology teaches that the finer the grains of a rock, the more likely it is
to contain evidence of past life. In fact, on Earth, small grains tend to settle in
low-energy environments such as the bottom of a pond, where they can preserve decaying
organisms or other signs of life settling there. On July 20, the rover set out to analyze the
collected material with a sophisticated scientific instrument called Scanning Habitable Environments
with Raman & Luminescence for Organics & Chemicals, or SHERLOC. And to everyone's surprise,
Wildcat Ridge turned out to be the richest sample of organics ever found on Mars so far.
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OK, but why is this so important? And what exactly is organic matter?
Organic molecules are made up of a wide variety of compounds consisting mainly of carbon and
usually also include hydrogen and oxygen atoms. In addition, they may contain other elements,
such as nitrogen, phosphorus, and sulfur. Although they may also be produced by chemical
processes that have nothing to do with biology, some of these compounds are considered to be true
biosignatures, that is, evidence that billions and billions of microorganisms once swarmed in
the waters of Lake Jezero, eventually ending their lives encompassed in the bottom sediments.
In practice, the most optimistic hypothesis is that In the distant past, the sand, mud,
and salts that now make up the Wildcat Ridge rock were deposited in an environment that could
potentially have supported life; and the fact that organic matter was found in a sedimentary
rock-a type that on Earth is synonymous with the fossilization of ancient biological
forms-is obviously very important. Does this mean that Perseverance
has found evidence of life on Mars? The answer is no. We cannot be sure.
As effective as the instruments aboard Perseverance are, coming to further conclusions
about the contents of the Wildcat Ridge sample will have to wait until their return to Earth
for a more in-depth study. Although as of now, there is at least the certainty that the river
delta within Jezero Crater contains exactly the type of sedimentary rocks for which Perseverance
was built and sent to this area of Mars. For this reason, the rover is equipped
with 43 titanium tubes in which it caches the Martian soil and rock it is studying.
So far, a dozen test tubes have been filled and sealed, and all will eventually be deposited
in a well-marked spot on the Martian surface. The project plans to collect at least 20 samples
to bring back to Earth in the future, although the researchers hope to be able to fill all 43 tubes.
Having collected the samples, the researchers will also have to decide where to have Perseverance
leave them on Martian soil. It is not yet clear whether they will have the cargo deposited in
one place, or whether they will decide to create at least two separate depots so that they will
have backup samples in case something goes wrong. The tubes are expected to ensure the integrity of
the samples for at least 20 years on Mars, a congruous amount of time for the development
of the recovery mission, about which there are still many questions to be answered.
In 2028, NASA and the European Space Agency will launch a Mars Sample Return Mission, which should
bring a new rover to Mars to retrieve the samples and load them onto a mini rocket, which should
then take them into orbit around Mars. At this point, a probe should intercept
the container with the tubes and bring it back to Earth.
Nothing like this has ever been attempted, but having those samples on our planet
would allow for much deeper and more precise analysis in search of clues to Martian life.
. That is the good news. The
less good news, or at least the less immediately gratifying, is that it will be a long time before
scientists can learn whether the ingredients of Martian biology actually signify the long ago (or
even existing) presence of Martian biology. In fact, samples are not expected to be delivered
to Earth until 2033 at the earliest. And this also means that the long-awaited
first human landing on the red planet will not take place before that date.
In the meantime, the scenario of the return of the samples is our best bet to find out
whether our once-watery planetary neighbor was also a living neighbor.
The just-announced Perseverance discovery raises the possibility, at least a little,
that the answer to that question may be yes.