The ongoing effort to under Martian geology and the planet’s history continues. A recent paper from a scientific team in China looks at the data collected by Zhurong, a rover that has been in place on the Red Planet since 2021. While it didn’t find any evidence of water in the basin it was looking in, it did find some interesting buried features and provided more data to our mounting understanding of one of our nearest neighbors.
When Zhurong touched down in May of 2021, it did so in Utopia Planitia, a large section of the Martian northern hemisphere equivalent to a plain on Earth. In the past, the Mars Reconnaissance Orbiter, one of the most prolific Martian discovery missions, found evidence of underground water nearby. It used radar, which is assumedly part of why the Chinese National Space Administration picked that location for a closed look with ground-penetrating radar mounted to a rover.
Unfortunately, Zhurong found no evidence to support water up to 80 meters under the surface of the 1.9 km path it walked through the plain. Nothing turned up on its two radar systems. One of those systems is sensitive but only can penetrate about 4.5 m of the surface, while the other could reach a much deeper 80 m but with a much lower resolution.
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A press release from the Geological Society of America pointed out that the Zhurong observations didn’t rule out the existence of water below the 80 m point. As such, the data from MRO might still be correct. But it seems it will be a challenge to get access to what, if any, water there is under the surface.
However, the data still had other exciting features – primarily crater walls. Many of these features were formed by asteroid impacts that blast through Mars’ paltry atmosphere to impact the ground but are slowly covered by dust during the global sandstorm events that occasionally sweep through Mars. So however pock-marked the planet’s surface looks, there are plenty of hidden craters beneath the surface.
This contrasts the Moon, where there’s so much debris sitting on top of the surface that the first 10 meters of lunar regolith show almost no features at all. While there are some features lower than 10 m, it begs the question – why are Martian craters so visible while lunar ones are not?
The most plausible explanation has to do with their atmospheres. Mars has an atmosphere, though it is only about 1% of the Earth’s. However, the Moon doesn’t have one at all. Micrometeroids, which are extraordinarily common in the solar system, would burn up in the Martian atmosphere. In contrast, on the Moon, they would impact the surface, sending dust spraying everywhere until it eventually settles back down – on top of some older craters that happen to be surrounding the new impact site.
While that is indeed a plausible theory, it has yet to be tested, but the data from Zhurong will provide important insight into the differences between these two surfaces. As rovers become more common on the Moon and Mars, humanity will soon better understand the geological forces on these heavenly bodies, even if most of the activity seems to come from space itself.
Geological Society of America – Complex subsurface of Mars imaged by Chinese rover Zhurong
Chen et al – Martian soil as revealed by the ground-penetrating-radar at the Tianwen-1 landing site
UT – China’s Zhurong Rover Looks Deep Underground and Sees Layers From Multiple Floods on Mars
UT – China Unable to Reestablish Contact With its Zhurong Mars Rover
An image of some of the features founds in the Martian sub-surface along with satellite imagery of the Zhurong rover’s path.
Credit – Chen et al.