by Stephen Clark
The
dark band near the top of this Nov. 18 image from Curiosity’s
navigation camera is part of the Bagnold Dunes. Credit: NASA/JPL-Caltech
The Curiosity rover’s next destination is a moving mound of
wind-blown dark sand blanketing the base of Mount Sharp, the focal point
of the Mars mission’s research, scientists said this week.
It will take a few days to reach the dunes, and rover drivers at
NASA’s Jet Propulsion Laboratory must be careful to avoid guiding
Curiosity too far into the dune field and getting stuck.
A similar predicament ended the mission of the Spirit rover,
Curiosity’s predecessor on the red planet, when it drove into a much
smaller sand trap in 2009. Engineers were never able to free the rover
from the sand pit, and the craft’s solar panels were pointed in the
wrong direction to collect energy from the sun as it fell low on the
horizon in the Martian winter.
Curiosity will not have the same pitfall as Spirit because it relies
on a nuclear power source, but an entangled rover would threaten the
future of the mission, which is in its fourth year.
Curiosity will be the first rover to explore an active Martian sand
dune up close. The rover is heading for a stretch of sand dunes called
the “Bagnold Dunes” named for Ralph Bagnold, a British military engineer
who pioneered research into how winds transport sand grains in the
early 20th century.
One of the dunes is as tall as a two-story building and as broad as a football field, according to a NASA press release.
Images from a sharp-eyed camera aboard NASA’s Mars Reconnaissance
Orbiter show the dunes are moving up to 1 metre (3 feet) per year,
scientists said.
As of Monday, Curiosity was about 200 metres (660 feet) from the dune
it is heading to first. The rover has completed further drives this
week.
“The Bagnold Dunes are tantalizingly close, and this week is mostly
focused on driving to the dunes.
On Sol 1167 (overnight Tuesday, U.S.
time), Curiosity drove 39 metres (128 feet), and the dunes are starting
to look pretty big,” wrote Lauren Edgar, a research geologist with the
U.S. Geological Survey and a member of the Curiosity science team, in a
blog post Wednesday.
Once Curiosity reaches the dunes, scientists plan to use the rover’s
robot arm to scoop a sample of sand for delivery to the craft’s internal
laboratory instruments. The rover will also use a wheel to dig into the
dune to reveal its interior, according to NASA.
Curiosity is slowly trekking up the foothills of Mount Sharp, a
three-mile-high peak inside Gale Crater, a basin excavated by an
asteroid or comet impact.
This
view from the Mast Camera (Mastcam) on NASA’s Curiosity Mars rover,
created using multiple images taken Sept. 25, shows a dark sand dune in
the middle distance. The rover’s examination of dunes on the way toward
higher layers of Mount Sharp will be the first in-place study of an
active sand dune anywhere other than Earth. Credit:
NASA/JPL-Caltech/MSSS
The dune campaign is a natural extension of Curiosity’s primary focus
of studying ancient geological processes that shaped rocks and made the
red planet habitable billions of years ago, scientists said.
“We’ve planned investigations that will not only tell us about modern
dune activity on Mars but will also help us interpret the composition
of sandstone layers made from dunes that turned into rock long ago,”
said Bethany Ehlmann, a scientist at the California Institute of
Technology and JPL.
The water flows and volcanism that carved giant channels and built
towering mountains on Mars in ancient times are no more. Winds are now
the most significant cause of Martian erosion, scientists said.
Wind measurements to prepare for the dune campaign have already
begun. Geologists hope to learn how much of a role wind played in
forming ancient sedimentary rocks like sandstone compared to the effects
of water in transporting sediments.
“We will use Curiosity to learn whether the wind is actually sorting
the minerals in the dunes by how the wind transports particles of
different grain size,” Ehlmann said in a NASA press release.
Researchers believe dunes on Mars behave differently than they do on
Earth. The surface pressure on Mars is about six-tenths of one percent
the pressure on Earth, with Martian gravity three times weaker than
Earth’s.
“These dunes have a different texture from dunes on Earth,” said
Nathan Bridges from the Johns Hopkins University’s Applied Physics
Laboratory, who leads dune campaign planning with Ehlmann.
“The ripples
on them are much larger than ripples on top of dunes on Earth, and we
don’t know why.
We have models based on the lower air pressure. It takes
a higher wind speed to get a particle moving. But now we’ll have the
first opportunity to make detailed observations.”
Reeves reached his theory after high-resolution images discovered
what he said were straight lines in King Tut's tomb. These lines,
previously hidden by color and the stones' texture, indicate the
presence of a sealed chamber, he said. The images were later broadcast
live on national television last September.
