With the imminent landing on Mars of both the American rover Perseverance only days away on February 18th followed by China’s rover in April, I think it time for a new rover update, not only providing my readers a review of the new landing sites but a look at the most recent travels of Curiosity on Mars and Yutu-2 on the Moon.

Curiosity

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The panorama above, made from four images taken by Curiosity’s right navigation camera on February 12, 2021 (found here, here, here, and here), looks south to the base of Mount Sharp, now only a short distance away. The yellow lines on the overview map to the right show the area this panorama covers. The white line indicates Curiosity’s previous travels. The dotted red line in both images shows Curiosity’s planned route.

The two white dots on the overview map are the locations of the two recurring slope lineae along Curiosity’s route, with the plan to get reasonable close to the first and spend some time there studying it. These lineae are one of Mars’ most intriguing phenomenon, seasonal dark streaks that appear on slopes in the spring and fade by the fall. There are several theories attempting to explain their formation, most proposing the seepage of a brine from below ground, but none has been accepted yet with any enthusiasm.

After leaving the edge of large dune field that the rover had been skirting, Curiosity is now very carefully working its way across a very rubbly terrain that marks the transition from the clay unit below to the sulfate-bearing unit above. Scientists suspect this is also the transition from regions that had water in the past to terrain that has always been dryer. Since this is a very important geological transition for understanding the past geological history of Gale Crater and Mars, the scientists are spending a little time here.

Not that they have much choice. The rubble is rough and sharp, and they need to move carefully to protect Curiosity’s fragile and already beaten up wheels. Though the engineers have done great work in the past four years preventing much additional damage, this terrain is the worst the rover has traveled through in a long time. Care must be taken.

The rover should pass through this rubbly zone in a few weeks, and soon thereafter will work its way to a point below the lineae, where I expect it will remain for at least several months. The scientists need to stay that long in order to detect any changes. They will not touch the lineae, however, out of fear that Curiosity, which never expected to see such a thing and was therefore not sterilized as thoroughly as necessary, will contaminate it.

After this the rover will work its way west along the base of the mountain, all on the lowest layer of the sulfate unit, until it reaches the entrance to Gediz Vallis Channel, an event that should occur in about a year or so. Once it enters that channel the rover will finally be on the mountain, in terrain that will be both stark and monumental. The channel itself is about 1,500 feet high and about that wide, so the view will not be unlike hiking through one of the slot canyons of the American southwest. The ground will be swirling layers of material, similar to the terrain seen at The Wave in northern Arizona.

The scientists can’t wait. Neither can tourists such as I.

Perseverance

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In only a few days, on February 18th, the new American rover Perseverance will come screaming through the thin Martian atmosphere to hopefully land softly and safely in Jezero Crater. The photo to the right shows the target zone for that landing, near or on the giant delta of material that appears to have flowed out of a break in the crater’s wall sometime in the far past. For a detailed look at what they hope to find when they land here, see this July 30, 2020 Behind the Black article. As I wrote,

The rover’s goal will be first to study the floor of the crater, then the delta itself, working its way uphill until it reaches the break in the crater rim where the flow had entered. The science team will then have the rover enter that canyon, continue working its way uphill to the west until it climbs up out of that meandering drainage canyon onto the rough cratered terrain beyond.

It will take years for Perseverance to make this journey. Hopefully it will be as hardy as Curiosity has been. One advantage it has is that its wheels have been redesigned, based on what was learned from Curiosity. They will likely be tougher.

China’s rover on the Tianwen-1 orbiter

China has not yet chosen a name for its Mars rover. Though it is already in orbit around Mars on the Tianwen-1 orbiter, it will not land until late April, as it is necessary to do further reconnaissance beforehand with the orbiter of the rover’s landing site. NASA by U.S. law cannot provide any help to China, and so China could not request high resolution images of its landing site from Mars Reconnaissance Orbiter (MRO). That site, as shown by the white cross in the MRO context camera mosaic to the right, is in the northern lowland plains of Utopia Planitia at about 25 degrees north latitude. It is generally flat and featureless, though there are craters and small ridges scattered about.

The white box indicates the one MRO high resolution image of this location as of October, when this precise location was first leaked to the press. Since then MRO has taken a few more pictures, but the Chinese engineers I am certain want to use their cameras on Tianwen-1 to get a more detailed look in order to pick the exact landing spot. Once they have done so, they will program the lander for what is presently scheduled as a late April landing. Once on the ground the rover has a planned 90-day mission, though hopefully it will last much longer.

Since the terrain here on Utopia Planitia is mostly flat, the view won’t be spectacular. However, at 25 degrees north latitude there is a slim chance that there might be an ice layer below ground. The rover has ground-penetrating radar sensors designed to look for that ice layer. What it finds will be its most important contribution to the study of Mars.

Present research suggests it will find no underground ice, since the data so far suggests that water ice is widespread in high latitudes but generally disappears at latitudes below 30 degrees. It will not be a disappointment if the rover confirms this, only proof that we are beginning to successfully map out the geology of Mars.

If it does find an underground ice layer, however, this discovery will force a major rethinking of that Martian geology.

Yutu-2

On February 7th Chinese engineers reactivated both the rover Yutu-2 and its lander Chang’e-4 to begin their 27th lunar day studying the far side of the Moon. Both had been planned for a nominal 90-day mission (in Earth days). They have both exceeded that by nine times.

Over that time Yutu-2 has traveled mostly west and slightly north of its landing site, covering about 2,062 feet. The goal, still about a mile away, is to reach a region of basalt lava. The rover travels about 100 feet per lunar day, so it is going to take a considerable time to get there, assuming it lasts that long.