The Curiosity rover has been actively exploring Mars for two years now, and as it celebrated its second anniversary on Tuesday, Aug. 5, it is also, after a lengthy journey, approaching its primary mission goal: the massive Mount Sharp in the middle of Gale crater.
Curiosity first landed on Mars on Aug. 5, 2012, PDT (Aug. 6, 2012, EDT) and has already immensely expanded our knowledge of the Red Planet, in particular its landing site in Gale crater. The roving laboratory has confirmed the previous existence of ancient riverbeds and a lakebed which used to fill portions of Gale crater billions of years ago.
While not directly looking for signs of ancient life, Curiosity has been studying the rocks and terrain for evidence of a previously habitable environment—the primary goal of the mission. According to scientists involved, it has already done that, in spades, and it didn’t even have to travel very far.
“Before landing, we expected that we would need to drive much farther before answering that habitability question,” said Curiosity Project Scientist John Grotzinger of the California Institute of Technology, Pasadena. “We were able to take advantage of landing very close to an ancient streambed and lake. Now we want to learn more about how environmental conditions on Mars evolved, and we know where to go to do that.”
In the Yellowknife Bay region, very close to the landing site, clay-bearing sedimentary rocks provided the evidence for an ancient freshwater lakebed, now long gone. Unlike the water at the Spirit and Opportunity landing sites, the water in Gale crater was non-acidic, just like water in most lakes on Earth, ideal for microbes if any ever existed. Rounded pebbles in the gravel also helped to confirm that a streambed once flowed through here, right where Curiosity landed. The dried-up streamed can still be seen from orbit, cutting through the crater rim. Curiosity landed on the alluvial fan where the water carried small pebbles and rocks, leaving gravel on the surface, just as rivers do on Earth.
All of this was accomplished during Curiosity’s first year on Mars. So what else is there to do? A lot. During the second year, the rover has continued to make its way toward its primary target, the looming Mount Sharp, which sits in the middle of Gale crater and stands 3.4 miles (5.5 kilometres) tall. The scenery alone is breathtaking, with mesas, buttes, and canyons, very reminiscent of the American southwest. But Mount Sharp is also an important science target, as there are more clay minerals in this region, and the many layers in the hills are a record of the environmental history as conditions changed from warmer and wetter to colder and drier over time.
Along the way, Curiosity has zapped rocks with its laser and drilled into some of them to further analyze their composition. While supporting the earlier water findings, detecting organics, another primary goal of the mission, has been elusive. Traces have been found, but not enough yet to determine how much organic material was in this region of Mars in the past, a critical clue to finding out whether life could have actually existed here.
Aside from some relatively minor computer glitches, Curiosity has remained pretty much trouble-free. The rover has been using its B-side computer since a problem occurred with its A-side computer in February 2013. A hiccup last week with the B-side computer was a cause for concern, but full functionality has now been restored. The only other significant concern has been damage to the wheels, from traversing some very rough terrain, with sharper and more pointy rocks than expected. This has caused some tears in the thin outer aluminum casing of the wheels, although rover engineers are confident it won’t affect the performance of the wheels or the rover itself too much. Some of the roughest terrain along the route was encountered recently at “Zabriskie Plateau,” which was largely unavoidable. To be safe though, Curiosity is now driving through softer, more sand terrain as much as possible.
According to Jim Erickson, project manager for Curiosity, “The wheels took some damage getting across Zabriskie Plateau, but it’s less than I expected from the amount of hard, sharp rocks embedded there. The rover drivers showed that they’re up to the task of getting around the really bad rocks. There will still be rough patches ahead. We didn’t imagine prior to landing that we would see this kind of challenge to the vehicle, but we’re handling it.”
As of now, Curiosity has just entered a network of shallow valleys, the first of which is called Hidden Valley. These sandy, drift-filled valleys continue southwest toward the base of Mount Sharp, which Curiosity will follow until it reaches the Murray Buttes, the entrance point to the mesas, buttes, and valleys at the base of Mount Sharp. Curiosity is still about 2 miles (3 kilometers) away from that location, but getting closer every day.
As Curiosity now celebrates its second year of Mars exploration, it is also now approaching the first bedrock which makes up part of the base of Mount Sharp itself. As Curiosity Project Scientist John Grotzinger of the California Institute of Technology, Pasadena, explained, “We’re coming to our first taste of a geological unit that’s part of the base of the mountain rather than the floor of the crater. We will cross a major terrain boundary.”
The closest outcrop of this new geological unit is less than 500 meters away and is being called “Pahrump Hills.” After doing its usual study and analysis of this outcrop, the rover will be on its way again, finally approaching the long-range mountain target that it has had in its sights for so long now. Once there, a whole new exploration phase will begin, as the rover makes its way among the hills and valleys which are reminiscent of the Grand Canyon in appearance.
Hopefully the bedrock and associated geology of Mount Sharp will provide more clues to the water-rich environment that used to exist here. How Mount Sharp itself formed is still a bit of a mystery to planetary scientists as well, as it looks somewhat out of place in the middle of a big crater. At some point in its history it was seemingly more of an island in Gale crater lake. With the lake(s) and rivers, Gale crater was once much more Earth-like and hospitable than it is now.
As a nuclear-powered rover not dependant on solar panels like Spirit and Opportunity, it is expected that Curiosity will be able to continue to explore this fascinating place on Mars for at least several more years, barring any tragic accidents or the like of course. The scenery in the foothills of Mount Sharp should be like none seen before in Mars exploration history.