You can’t always get what you want …

CuriosityAugust 5th marked the 2nd anniversary on Curiosity’s landing on Mars. The “landiversary”, as NASA dubbed the occasion, passed in something of a subdued manner in many respects, featuring a re-run of the August 2012 video reviewing the MSL’s arrival on Mars. Reviews of the mission from the perspective of two years on from that remarkable lading didn’t start-up until the days after the anniversary, with videos and lectures from members of the mission team.

One of the films which did appear, directly out of Caltech, rather than NASA’s Jet Propulsion Laboratory (which is located on Caltech’s Pasadena, California, campus), is Our Curiosity, a 6-minute celebration of Curiosity’s mission, and humanity’s drive to explore, to seek, to learn, and to understand, narrated by Felicia Day and the superb Neil DeGrasse Tyson.

August 5th also marked my last MSL report, when Curiosity was some 3 kilometres from the lower slopes of “Mount Sharp”, the huge mound at the centre of Gale Crater, and the rover’s primary target for exploration. At that time, the rover had started to cross a region of chaotic terrain, marked by a rocky plateau cut by a series of sandy-bottomed valleys. The plateau itself proved to be littered with sharp-edges rocks and stones which had already caused some increase in the wear and tear being suffered by the rover’s wheels – albeit not as much as mission engineers had feared – by the time Curiosity had reached the edge of the nearest of the shallow valleys, which had been dubbed “Hidden Valley”.

The plan had been to use the valleys, where the sand would be less wearing on the rover’s aluminium wheels, to reach an exposed area of bedrook designated the “Pahrump Hills”, where Curiosity would engage in further rock sampling work prior to it continuing on to the “Murray Buttes”, the entry point for its ascent up the lower slopes of “Mount Sharp”.

However, rather than drive the one-tonne rover straight through the middle of the valley, where there are numerous dunes of potentially soft, wind-blown sand which might cause some difficulty traversing, the idea had been for Curiosity to skirt along the edge of the valley, where it was hoped the sand would be firmer and make for a better driving surface. Unfortunately, this proved not to be the case; as the rover proceeded along “Hidden Valley” it exhibited far more signs of wheel slippage than had been anticipated, giving rise to fears that it might get bogged-down in the sand were it to continue.

The sands of Mars: an image from Curiosity’s black and white Navcam system captured on August 4th, showing the loose sands the rover was traversing as it continued into “Hidden Valley” (click for full size)

As a result, the rover reversed course, driving back out of the valley. In doing so, it crossed the rocky “ramp” it had used to originally enter the valley, and one of its wheels cracked the slab-like rock’s surface, revealing bright material within, possibly from mineral veins. The rock, dubbed “Bonanza King” showed similar signs of origin as “Pahrump Hills”, so a decision was made to examine it as a possible substitute drilling site.

“Geologically speaking, we can tie the Bonanza King rocks to those at “Pahrump Hills”. Studying them here will give us a head start in understanding how they fit into the bigger picture of Gale Crater and Mount Sharp,” said Curiosity Deputy Project Scientist Ashwin Vasavada, before continuing, “This rock has an appearance quite different from the sandstones we’ve been driving through for several months. The landscape is changing, and that’s worth checking out.”

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