Summary: Curiosity remains on Vera Rubin Ridge, though it has begun moving toward the point where it will move down off the ridge. Opportunity remains in Perseverance Valley, though it has finally taken the north fork down.
Before providing today’s update, I have decided it is time to provide links to all previous updates, in chronological order. This will allow my new readers to catch up and have a better understanding of where each rover is, where each is heading, and what fascinating things they have seen in the past year and a half.
These updates began when I decided to figure out the overall context of Curiosity’s travels, which resulted in my March 2016 post, Pinpointing Curiosity’s location in Gale Crater. Then, when Curiosity started to travel through the fascinating and rough Murray Buttes terrain in the summer of 2016, I stated to post regular updates. To understand the press releases from NASA on the rover’s discoveries it is really necessary to understand the larger picture, which is what these updates provide. Soon, I added Opportunity to the updates, with the larger context of its recent travels along the rim of Endeavour Crater explained in my May 15, 2017 rover update.
- Curiosity update: July 7, 2016: Balanced rock on Mars
- Curiosity update: July 24, 2016: Curiosity’s way forward
- Curiosity update: July 28, 2016: Heading directly for Balanced Rock
- Curiosity update: August 11, 2016: Curiosity prepares to move on
- Curiosity update: August 16, 2016: Balanced Rock at last
- Curiosity update: August 22, 2016: Beyond Murray Buttes
- Curiosity update: August 28, 2016: The alien buttes of Mars
- Mars rover update: September 6, 2016. The first update including Opportunity.
- Mars rover update: September 13, 2016. The first official update.
- Mars rover update: September 20, 2016
- Mars rover update: Sept 27, 2016
- Mars rover update: October 6, 2016
- Mars rover update: November 3, 2016
- Mars rover update: November 14, 2016
- Mars rover update: December 22, 2016
- Mars rover update: January 18, 2017
- Mars rover update: February 14, 2017
- Mars rover update: April 21, 2017
- Mars rover update: May 15, 2017
- Mars rover update: June 23, 2017
- Mars rover update: July 12, 2017
- Mars rover update: August 11, 2017
- Mars rover update: September 6, 2017
- Mars rover update: November 16, 2017
- Mars rover update: December 18, 2017
- Mars rover update: January 16, 2018
Now to talk about the most recent news from both rovers!
In the past few weeks the Curiosity science team has begun moving the rover eastward, back towards its planned route off of Vera Rubin Ridge, which is geologically dubbed the Hematite Unit. The image below, cropped, reduced, and annotated from the full orbiter traverse map, shows its actual path (yellow dotted line) compared to my rough estimate of the planned route (red dotted line), based on this October 3, 2016 press release.
The detour occurred because the team wanted to get some close looks at some lighter patches of ground, as seen in the orbit images. Today, they issued a press release, noting some of the strange crystal features spotted in these patches.
The team drove the rover to a site called “Jura” in mid-January to examine an area where — even in images from orbit — the bedrock is noticeably pale and gray, compared to the red, hematite-bearing bedrock forming most of Vera Rubin Ridge. “These tiny ‘V’ shapes really caught our attention, but they were not at all the reason we went to that rock,” said Curiosity science-team member Abigail Fraeman of JPL. “We were looking at the color change from one area to another. We were lucky to see the crystals. They’re so tiny, you don’t see them until you’re right on them.”
The features are about the size of a sesame seed. Some are single elongated crystals. Commonly, two or more coalesce into V-shaped “swallowtails” or more complex “lark’s foot” or star configurations. “These shapes are characteristic of gypsum crystals,” said Sanjeev Gupta, a Curiosity science-team member at Imperial College, London, who has studied such crystals in rocks of Scotland. Gypsum is a form of calcium sulfate. “These can form when salts become concentrated in water, such as in an evaporating lake.”
During the last two weeks a number of amateur observers who like to daily check out Curiosity’s raw images, including regular reader and contributor Phil Veerkamp, noticed some strange fossil-like features in one image. Below is that image, with four of the features highlighted in yellow and three shown in close-up insets to the right.
For four similar looking features to be seen on the surface of Mars sure was intriguing. I put out some feelers to the Curiosity science team, and got a simple explanation. There were produced by the rover’s laser, ChemCam, which is used to obtain spectroscopy. As Jeff Johnson from Johns Hopkins University Applied Physics Laboratory explained, “The locations correspond precisely to where the laser shots hit, so we’re confident in their cause. The areas affected are slightly larger than normal and the ChemCam team is studying the potential cause.”
That the features are all in a line also strengthen the science team’s conclusions. The strange shape, which doesn’t really resemble other ChemCam shots, might tell us something about the geology, or the laser itself, though Roger Wiens, ChemCam’s principle investigator, emailed me to say that the laser is in fine shape and these shapes suggest no problems.
Such features are a warning to amateurs: Don’t jump to conclusions. Sometimes what seems exotic is merely pedestrian, and a little digging will uncover that fact.
In its upcoming journey, Curiosity moves downhill off of Vera Rubin Ridge, and out into the clay unit, heading towards a canyon and the far rougher terrain leading uphill onto Mount Sharp, as shown by the image below, taken on Sol 1949. I expect the landscape images coming from the rover in the next few months should be quite exciting.
Opportunity’s travels at the moment remain limited because it is winter and the rover can only store so much power. When they move the rover they do so in small increments, aimed at finding good locations where its solar panels will be angled well for more sunlight.
Since July Opportunity has been working its way downhill in Perseverance Valley, a gully that in orbital images looks like it could have been formed from either water flow, ice flow, or wind. Though close-up images of the ground actually appear to resemble slickenslides, features that on Earth suggest ice erosion, the science team so far seems to favor wind.
In December they were considering whether to take a north or south fork, heading downhill, as shown in the traverse image on the right above. In January they decided to take the north fork, and began working the rover into it. The image to the right looks uphill to the west at the rover’s tracks. You can see where it turned north and then headed downhill.
Eventually, they plan to move the rover out onto the floor of Endeavour Crater, to the east. Whether will do this directly from Perseverance Valley, or continue working south along the rim before doing so, is as yet unclear. Before that decision has to be made, however, they still have a lot to explore in the valley, especially as they move east and north into the outlet flows shown in the upper right corner of the larger traverse map, above.
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