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You might have heard that there’s an alien world out there
populated only by robots.
…Mars. It’s Mars.
Among that population are three rovers on its surface, working hard right now to
help humanity understand what our planetary next door neighbor is like now…
as well as what it used to be like in the past.
NASA has sent loads of missions that have gotten loads of attention,
from Sojourner in the 1990s, to its newest roving expat, Perseverance.
But there’s one mission you may not have heard of,
one that has already spent over a year on the Martian surface.
It’s China’s Zhurong rover.
And it’s bringing us ever closer to understanding the history
of the fourth planet from the Sun.
Tianwen-1 is China’s first independent interplanetary mission,
using an orbiter and rover to explore the red planet.
The orbiter is also named Tianwen, which means “Questions to Heaven”,
while the rover is Zhurong, after the Chinese god of fire.
They launched together, back in July 2020, in the very same launch window
as both Perseverance and the United Arab Emirates’ Hope orbiter.
Both orbiter and lander entered Martian orbit the following February.
Then in May, Zhurong broke away and fell to the surface,
landing in the Utopia Planitia basin.
That made China just the third country to complete a soft landing on Mars,
after the US and USSR, but the second to have an operational spacecraft…
because the Soviets lost communications with theirs soon after landing.
Utopia Planitia is the largest impact basin in Mars’s northern lowlands,
and Zhurong is the first craft to explore the southern part of this region up close.
While the exact origins of these lowlands are still being debated,
most of it looks like it formed about 3.34 billion years ago.
When you’ve got a rocky body floating out there in space, it’s going to get hit
by debris over time. So the more craters a patch of crust has, the older it is.
Based on the low crater count in Zhurong’s location,
at least some of Utopia Planitia could be as young as 700 million years old.
In other words, the surface may have been wiped clean or renewed somehow.
Originally slated for a three-month mission,
Zhurong is still going strong as of this writing, one year later.
But over the past year, Zhurong has been busy using its six scientific instruments
to peel back the layers of the Martian surface and subsurface.
In one case that’s metaphorical, because it has ground penetrating radar.
In another it’s more literal, because it has a laser it uses to vaporize
the outer layers of rock samples to figure out what minerals they’re made of.
The Tianwen orbiter, meanwhile, has the job of relaying all that precious data back to Earth.
But it was also used to help confirm exactly where Zhurong was going to land,
and is also now doing some science of its own.
And the results of all this sciencing are slowly rolling out.
Like based on how well the rover’s wheels could traverse the surface,
scientists were able to show that the surface
acts basically like compact, sandy soil does on Earth.
But overall, it looks like this region of Utopia Planitia has a thin layer of dust and
sand sitting on top of a layer of rock known as duricrust: a hardened mix of silicon,
aluminum, and iron-based minerals that have cemented together.
At least on Earth, this happens after the minerals are deposited
by a body of water, which then evaporates.
In other words, it’s yet another piece of evidence that Mars used to be swimming in liquid water.
But one study published in May 2022 using Zhurong’s data revealed that that liquid
water may have been in the area way more recently than scientists thought it was.
The research team identified a sample of rocks which look to have come
from the duricrust, and attempted to work out what minerals they were made of.
Unfortunately, they weren’t able to pin the exact minerals down, but they did figure
out that they had water molecules incorporated into their structure.
Whether or not this duricrust material is related to other geologic features
in the area is currently unknown.
We also don’t know exactly how the duricrust in this area formed.
One possibility is that it was created by groundwater
rising up from a lower layer, then evaporating.
Another is that the water came from subsurface ice that melted due to
a sudden change in temperature caused by volcanism or meteoric impacts.
Or the ice could have been melted by a temporary infusion of local liquid water.
In that case, the effect would be a lot more limited in size,
so an easy way to rule that out would be to send Zhurong further away
and see if the same duricrust rocks formed over yonder.
Whatever the cause, the presence of this kind of rock, in this much younger region
of Utopia Planitia, suggests that Mars was a bit wetter, at least for longer,
than scientists have thought.
While Zhurong continues its investigation into Mars’s past,
scientists on Earth are looking for ways to keep in contact with the little rover
while the Tianwen orbiter is busy sciencing.
Last year, the European Space Agency tried linking Zhurong up with their orbiter, Mars Express.
You might think that’d be as easy as just dialing someone else’s phone number,
but the two communications platforms aren’t actually immediately compatible.
Out of five tests, only one was successful at sending non-corrupted data.
So we’ll have to wait to hear if these two space agencies
make more progress on that collaboration.
Meanwhile, we can celebrate this little guy’s achievements.
And you can even take Zhurong home with you as this month’s Pin of the Month!
This year, our pins are celebrating the best in solar system exploration,
and this month only, you can pre-order this pin to add to your collection.
We’ll take pre-orders all this month, after which we’ll close orders,
make the pins, and ship them to you.
After that, you can never get this one again…
but you can get next month’s awesome pin, so keep your eyes peeled for that.
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