Thanks to Grammarly for sponsoring today’s video. “After successfully landing on an alien planet,
the protagonist began the search for alien life.” This may sound like a line from a
science fiction drama, but it’s actually based on real life events, and they are still ongoing.
The protagonist in question is the Perseverance Rover, the alien planet is Mars, and the life
it’s searching for are the fossilised remains of ancient bacteria from millions of years ago.
In mid-2021 it attempted to collect rock samples which could contain precious evidence that life
can indeed form on other planets; that we are not alone in this universe. But when you are entering
the uncharted, it’s what you don’t know that poses the greatest risks. I’m Alex McColgan, and you
are watching Astrum. Join with me in the third video in this series, as we explore the months
of June to September 2021 of the Perseverance Mars mission, which covers the rover’s first attempts
at collecting samples on Mars. And I’m afraid to say, things were about to not go as planned.
Perseverance landed on Mars in February 2021. Unlike the rovers that had gone on before,
it was not primarily designed to find evidence of conditions that might allow life to thrive.
Perseverance was here for the real deal. Its mission was to find life on Mars, but it did not
begin right away. After an incredibly successful landing, it spent the next 4 months staying fairly
near its landing site, testing its equipment and helping another machine on Mars – the
small Ingenuity drone helicopter – to carry out its mission. We covered this time period in the
last video, which you can check out here. Now, it was finally time for the Perseverance Rover to do
what it had come here for – to begin its hunt for rock samples in order to locate alien life.
And to that end, on the 1st of June, it set off travelling on its path through Jezero crater.
Millions of years ago, a massive object had crashed into the surface of Mars.
The resulting crater was hundreds of meters deep and 40km in diameter, and due to the
different geological conditions that existed back then, it soon begun to fill up with water.
In time this crater became a massive lake and earned the name “Jezero” - which
(somewhat unimaginatively) literally means “lake” in some of the Slavic languages.
Massive rivers began to run into the Jezero crater, carving valleys through the terrain
and depositing all the resulting silt over huge deltas. This is why Jezero was selected
as the site for Perseverance’s mission. If life worked the same way here as it does on Earth,
this location would be rife with possibilities for the emergence and propagation of life.
As Mars is now a barren wasteland, the kinds of things Perseverance is looking for
would not be immediately obvious. Any life that swam in Jezero’s lake would have lived, died,
and fallen to the lakebed where accumulated silt from the river would have buried it in hard rock.
So, to help it complete its mission, Perseverance came equipped with a drill mounted on a 2m long
robotic arm, capable of either abrading away surface rock to reveal their inner layers, or even
coring samples of that same rock about the size of a stick of chalk and placing it in a sealed tube.
With its ultraviolet spectrometer SHERLOCK or its X-ray fluorescence spectrometer PIXL, Perseverance
has the cameras and tools it needs to find, image and collect samples for later retrieval back to
Earth. However, it is important to choose targets carefully. Perseverance has limited
resources available to it – it only has just over 30 sample tubes for storing rock cores for the
return journey home. Tempting as it might be to just grab a sample from right where it landed,
Perseverance needed to only collect samples from the locations most likely to provide evidence of
signs of life, or offer particular insight into the formation and age of Jezero crater to pinpoint
better possible locations for later. As such, Perseverance did not start drilling immediately,
but instead began travelling south from its landing location at Octavia E Butler Landing
(named after the science fiction author) to the area known as the Cratered Floor Fractured Rough.
Although this location was a little more than a kilometer away from Perseverance’s landing site,
Perseverance would not arrive at this new location for nearly 60 days.
This is because the unfamiliar, rocky surface of Mars is strewn with obstacles for a rover.
You’ll notice the rocks that are scattered over the Martian surface.
Perseverance would need to pick its path carefully around these, as the rover’s 52.5cm diameter
wheels can only drive over objects that are so large. Soft terrain poses just as many dangers.
The previous Martian rover Spirit came to an unfortunate end after getting stuck in
a sand dune. So, choosing its path is a balancing act – not too hard and rocky,
but also not too soft. And in the past, these decisions would have to be made on earth,
with a 20-minute average signal delay. No wonder the previous rovers had travelled so slowly.
However, Perseverance had gotten an upgrade compared to Spirit and Opportunity.
Advanced AI software called Autonav on the Perseverance rover allows it to map out its
surrounding environment and choose for itself the best path through it. Although there is still
some oversight from Earth, this greater degree of independence – which Perseverance can do on
the fly, while driving – allows the Perseverance rover to travel 6 times faster on average than the
speeds of rovers like Curiosity. This brings its top speed to an astounding… 0.12km/h. All
right, this is still not that fast. I did say that it took nearly 60 days to get a little
more than a kilometres’ distance. However, this is still a significant improvement,
and allows for more science to get done. And speaking of science, on the 20th of July,
Perseverance successfully managed to navigate its way to Cratered Floor Fractured Rough.
Taking things slowly, scientists picked out a rock to first test Perseverance’s abrading drill
systems. The abrade attempt took place on a paving stone nicknamed “Guillaume” and was a simple
success. The drill cut away the top and gave scientists insight into the kinds of stones that
Perseverance was driving on. By examining grain sizes, chemical composition, and other details,
scientists could gain insights into the types of rock these were – either sedimentary, the kind
likely to contain fossilised remains and other artifacts, or igneous rock formed from magma.
What they saw heartened them, and on the 6th of August, scientists picked out
another target rock – nicknamed “Roubion” – to take their first actual core sample.
Due to the time zones involved, it was 2am Pacific Daylight Time when over 90 engineers
and scientists gathered online to witness the fruits of their years of labour. Perseverance
cored successfully down to the 7 cm depth it had been programmed to reach. It photographed
the hole afterwards, and everything seemed to be going fine. Over the next 6 hours,
Perseverance painstakingly took the core, placed it in one of its tubes, and moved
it to its ACA (Adaptive Caching Assembly, the place where core tubes are processed).
Due to the nature of the mission, it’s vitally important that no contaminants be allowed to enter
the tube, or else it might invalidate the entire process. Finally, Perseverance transferred the
now-sealed tube to its storage unit. Scientists were elated at this perfect first-time success.
But then more data came through, and scientists realised that there was a problem.
The sealed tube was empty. Confusion filled them. Where had the sample gone? Due to the
limits of technology, scientists could not record on camera every movement of Perseverance.
It only has so many cameras. So, they had to rely on Perseverance to follow the orders they sent it.
But here it seemed that Perseverance had followed its orders, and yet the weight sensors in the
storage unit informed them that the tube was missing any additional weight – the core was gone.
Perseverance drove backwards, and looked between its tracks, but there was no sign
of a dropped core. In time, scientists arrived at a bittersweet conclusion. Perseverance had
not malfunctioned or done anything wrong – it was the rock itself that was to blame.
In the act of drilling, the unique nature of the Roubion rock meant that it was so
crumbly that when Perseverance had gone to pick the core sample up,
it had completely turned to dust. Perseverance could not collect it in that state.
Scientists had tested Perseverance’s coring on a hundred different types of rock on Earth,
and it had never encountered a problem like this before. Every other rock had been cored
successfully. So, while this was good, because it meant that Perseverance was not broken,
it cast a shadow over the rest of the mission – would all the rocks Perseverance encounters
be failures like this? However, NASA was not about to give up without trying. They reasoned that the
rocks in this area were likely just particularly weathered, and other rocks on Mars might hold
themselves together better. It was with renewed determination that Perseverance had another go.
Casting its camera around, Perseverance spotted some rocks 150m away that were as different
from the crumbly paving stones as possible. Scientists nicknamed these new rocks “Citadelle”,
which is French for castle, possibly hoping for something a bit more fortified this time.
As these rocks were sticking up from the landscape, it seemed reasonable that they
were made from sturdier stuff than the flat paving stones. If they resisted erosion,
they might do a better job of holding themselves together under a drill. Perseverance trundled
over to the ridge and primed itself for another attempt. On the 1st of September, NASA once again
held its breath as Perseverance attempted its second core attempt. You really get a sense of how
painstaking this process is, given the month-long gap between each attempt. Everything on Earth has
to be checked and double checked, every scrap of data analysed for the perfect conditions.
Every decision is carefully thought out and discussed. Would it work on the second attempt?
Perseverance’s drill collected a core that was 6 cm long. And, possibly with wry exasperation,
before sealing the core in a tube, Perseverance brought it round and added an additional step.
It took a photo of what it held, to confirm to everyone on Earth that it actually was holding
a core this time. And sure enough, it was. Scientists must have felt a huge relief as data
came back that Perseverance had successfully taken the core and transferred it to its storage area.
The core, nicknamed Montdenier, was ready to be taken back to Earth on a future mission,
where in a larger lab its secrets could be better analysed. Perseverance took another core
sample that day, just to be absolutely certain. They were possibly feeling on a bit of a roll.
And who can blame them? We are now one step closer to knowing whether life ever existed on Mars.
Although this sample is just the beginning and may not have any signs of life in it, we have stepped
a little further into the uncharted and know a little more. It will still have to be analysed.
We’ve not proven anything yet. But as long as there are still empty tubes to be filled and
energy in its battery, Perseverance’s mission to find evidence of alien life will continue.
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