DETROIT – You’ve heard the talk about returning to the moon. There's also been talk about sending people to Mars. But these missions are years in the future. While scientists work on those long-term projects, it’s easy to forget that there are amazing rovers still doing important research on the red planet (with more in the works). And NASA’s Curiosity rover, now in its seventh year on Mars, is still conducting important research.
The rover has been examining Gale Crater for a while, and is now halfway through a region scientists call the "clay-bearing unit" on the side of Mount Sharp, inside of the crater. The area in the spectacular photo above is an outcrop called Teal Ridge.
Billions of years ago, there were streams and lakes within this crater. Water altered the sediment deposited within the lakes, leaving behind lots of clay minerals in the region. That clay signal was first detected from space by NASA's Mars Reconnaissance Orbiter (MRO) a few years before Curiosity launched.
Rock samples that the rover has drilled here have revealed the highest amounts of clay minerals found during the mission. But Curiosity has detected similarly high amounts of clay on other parts of Mount Sharp, including in areas where MRO didn't detect clay. That's led scientists to wonder what is causing the findings from orbit and the surface to differ.
The science team is thinking through possible reasons as to why the clay minerals here stood out to MRO. The rover encountered a "parking lot full of gravel and pebbles" when it first entered the area, said campaign co-lead Valerie Fox, of Caltech.
One idea is that the pebbles are the key: although the individual pebbles are too small for MRO to see, they may collectively appear to the orbiter as a single clay signal scattered across the area. Dust also settles more readily over flat rocks than it does over the pebbles; that same dust can obscure the signals seen from space. The pebbles were too small for Curiosity to drill into, so the science team is looking for other clues to solve this puzzle.
Curiosity exited the pebble parking lot back in June and started to encounter more complex geologic features, including a stop to take the 360-degree panorama of Teal Ridge.
More recently, it took detailed images of Strathdon, a rock made of dozens of sediment layers that have hardened into a brittle, wavy heap. Unlike the thin, flat layers associated with lake sediments Curiosity has studied, the wavy layers in these features suggest a more dynamic environment. Wind, flowing water or both could have shaped this area.
(Closeup photos of “Srathdon,” a rock on Mars made up of many hardened sediment layers.)
Both Teal Ridge and Strathdon represent changes in the landscape. "We're seeing an evolution in the ancient lake environment recorded in these rocks," said Fox. "It wasn't just a static lake. It's helping us move from a simplistic view of Mars going from wet to dry. Instead of a linear process, the history of water was more complicated."
Indeed, Mars’ entire history is complicated. But scientists are making progress, and we now know that water once existed on the red planet. Hopefully, future exploration will determine if primitive life itself existed in those waters.