On September 15, the Curiosity Rover on Mars wheeled past a particularly beautiful rock formation. Curiosity took a series of photos with its 2-megapixel MastCams which graphic designer Ed Truthan stitched together to give us earth-folk a full view of the mass of rock. The rock was nicknamed Hottah and serves as the first in a series of recent discoveries placing an abundantly flowing river in the middle of the Gale crater Curiosity is exploring.
Huzzah looks “like someone came to the surface of Mars with a jackhammer,” said John Grotzinger, a project scientist for the mission, at a NASA press conference on Sept. 27. To me, it looks more like a fractured slab on concrete. As the 2.5 billion dollar roving science lab inspected Huzzah is was able to determine the rock was a composite of smaller rocks (or clasts). These tiny rocks that built up Huzzah were rounded and smooth suggesting one of two things: they experienced wind or water erosion. “The shapes tell you they were transported and the sizes tell you they couldn’t be transported by wind. They were transported by water flow,” said Rebecca Williams, a scientist on the Curiosity project at the Planetary Science Institute in Arizona.
In further exploration, Curiosity found a group of clasts that had fallen to the ground or otherwise detached from the composite rock. This formation was dubbed Link and is made of the same type of never-before-seen-on-Mars rock as Huzzah.
Orbital cameras above the martian surface photographed an alluvian fan in the region which denotes an area where debris has been spread across. With the evidence stacking up, it seems to be clear this fan represents a watershed where the river would have expanded as it flowed down in elevation. As the evidence piles up, NASA researchers are confident a ankle-to-waist deep river flowed through the area at around 2 miles per hour for a prolonged period of Mars’s past.
This isn’t the first indication of water or rivers found on Mars but it is the closest comparison to terrestrial flow back on Earth. In the 1970s NASA’s Mariner 9 orbiter arrived during a month-long storm covering the whole planet but, when the dust cleared, found a landscape deeply carved by a system of rivers. Later, the Phoenix lander found more evidence for water on Mars from exploration of the planet’s Arctic region.
Curiosity’s destination is Mount Sharp where clay and sulphate minerals have been seen from orbit—both essential to sustaining life. “A long-flowing stream can be a habitable environment. It is not our top choice as an environment for preservation of organics, though. We’re still going to Mount Sharp, but this is insurance that we have already found our first potentially habitable environment,” explains Grotzinger.
Curiosity still has a lot of analysis and exploration to do, but we’re already more acutely aware of Mars’s wet and possibly fertile past.