NASA's Curiosity rover has come a long way since touching
down on Mars seven years ago. It has traveled a total of 13 miles (21
kilometers) and ascended 1,207 feet (368 meters) to its current location. Along
the way, Curiosity discovered Mars hadthe conditions to
support microbial lifein the ancient past, among other things.
And the rover is far from done, having just drilled its
22nd sample from the Martian surface. It has a few more years before its
nuclear power system degrades enough to significantly limit operations. After
that, careful budgeting of its power will allow the rover to keep studying the
Red Planet.
Curiosity is now halfway through a region scientists callthe
"clay-bearing unit"on the side of Mount Sharp, inside ofGale
Crater.
Billions of years ago, there were streams and lakes within the 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.
"This area is one of the reasons we came to Gale
Crater," said Kristen Bennett of the U.S. Geological Survey, one of the
co-leads for Curiosity's clay-unit campaign. "We've been studying orbiter
images of this area for 10 years, and we're finally able to take a look up
close."
Rock samples that the rover has drilled here have revealedthe
highest amounts of clay mineralsfound 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 the campaign's other 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. It stopped to take a 360-degree
panorama at an outcrop called "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.
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."
Curiosity is discovering a richer, more complex story behind
the water on Mount Sharp - a process Fox likened to finally being able to read
the paragraphs in a book - a dense book, with pages
torn out, but a fascinating tale to piece together.
NASA's Jet Propulsion Laboratory in Pasadena, California,
leads the Mars Science Laboratory mission that includes Curiosity.
For more about NASA's Curiosity Mars
rover mission, visit:
News Media Contact
Andrew Good
Jet Propulsion Laboratory, Pasadena, Calif.
818-393-2433
andrew.c.good@jpl.nasa.gov
2019-157
Read More
No comments:
Post a Comment