Tag Archives: aeolis mons

Strata at Base of Mount Sharp

Ingenious new technique shows Mars’ Mount Sharp to be very porous

Some outside-the-box thinking allowed NASA to calculate the density of Mount Sharp on Mars — and the results aren’t at all what they expected.

Strata at Base of Mount Sharp

A view from the Kimberly formation on Mars taken by NASA Curiosity rover. The strata in the foreground dip towards the base of Mount Sharp.
Image credits NASA / JPL-Caltech.

Curiosity has been on a lonely trek on the surface of Mars for almost a decade now. It landed there in 2012 and has been exploring the planet ever since. But its journey is teaching us a lot about our galactic neighbor, including the surprising porosity of its rocks.

Mount Sharp, Mount Porous

“What we were able to do is measure the bulk density of the material in Gale Crater,” says Travis Gabriel, a graduate student at the Arizona State University School of Earth and Space Exploration, who computed the densities of the rocks Curiosity has been driving over.

I really like this study. For starters, Curiosity wasn’t ‘meant’ to be able to measure the densities of huge bodies of rock when it was designed — at least, not in the way the team did it.

First off, some context: Curiosity can be used to estimate rock density, but this is based on chemical analysis of rocks it can actually bore through (so it’s limited to making surface measurements). Gale Crater (wherein Mount Sharp, officially “Aeolis Mons”, nestles) definitely qualifies as a ‘huge body of rock’ with its 96-mile (154 km) diameter, and its depths are definitely out of Curiosity’s reach.

To estimate densities, the rover will essentially dig into a rock, take out the residue, and analyze its mineralogical composition. Based on the particular species identified and their ratios, ground control can then estimate how dense said rock is. And NASA was content with this for the longest time. But the present study casts doubt on those previous estimates.

“Working from the rocks’ mineral abundances as determined by the Chemistry and Mineralogy instrument, we estimated a grain density of 2810 kilograms per cubic meter,” Gabriel says. “However the bulk density that came out of our study is a lot less — 1680 kilograms per cubic meter.”

What the team did instead was to use Curiosity’s accelerometers and gyroscopes to read densities. These devices are pretty much exactly like that in any smartphone (only more accurate and expensive), and are used to determine Curiosity’s orientation and its motions. NASA uses readings from these devices to steer Curiosity across the face of Mars, just like you’d use those in your smartphone to steer towards the nearest pub.

These devices work round-the-clock, however — not just when you’re on the move. And those on Curiosity are sensitive enough to pick up on the local gravitational tug at whichever spot it finds itself on.

The team took engineering data beamed back by Curiosity ever since 2012, when it touched down on Mars. These readings were crunched to produce measurements of gravitational forces in more than 700 points across the rover’s track. The readings revealed that as Curiosity began ascending Mount Sharp, it started experiencing higher gravitational pulls. Which was expected.

But the increase was far weaker than what we’d expect to see in such a case, the authors report.

“The lower levels of Mount Sharp are surprisingly porous,” says lead author Kevin Lewis of Johns Hopkins University.

“We know the bottom layers of the mountain were buried over time. That compacts them, making them denser. But this finding suggests they weren’t buried by as much material as we thought.”

The findings help flesh out our understanding of how Mount Sharp came to be. Martian craters the size of Gale have central peaks raised by the very impact that scooped out the crater (Gale’s is Mount Sharp). So we know why Sharp is so tall. Its top layers also seem to be made out of wind-swept sediments, which are more easily eroded than rock. The prevailing theory up to now was that these sediments pressed down on the Mount and crater, compressing them into hardier rock, before eventually being swept away by the wind.

But the new findings suggest Mount Sharp’s lower layers have been compacted by only a half-mile to a mile (1 to 2 kilometers) of material — much less than if the crater had been completely filled.

“There are still many questions about how Mount Sharp developed, but this paper adds an important piece to the puzzle,” said Ashwin Vasavada, Curiosity’s project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California, which manages the mission.

“I’m thrilled that creative scientists and engineers are still finding innovative ways to make new scientific discoveries with the rover.”

This is definitely an interesting find — one that points to even more secrets yet to be unlocked on the slopes of Mount Sharp. The study also produced a powerful technique that NASA can use with Curiosity and future rovers to investigate far-off worlds. In essence, it’s pretty much the same principle as that used in gravimetry, but I definitely like seeing how much creativity the team brought to this study.

The paper “A surface gravity traverse on Mars indicates low bedrock density at Gale crater” has been published in the journal Science.

Curiosity’s search for Martian life may come up dry

Life on Mars

mount sharpThe sedimentary processes on Mars have generally been governed by wind, not water – but is this the case where the Curiosity rover is searching for life at the moment. If this is the case (and Curiosity will either confirm or infirm this when it reaches Mount Sharp next year), then odds are it won’t be finding any signs of Martian life – even if such life exists/existed on the Red Planet.

Last August, Curiosity landed inside the 154-kilometre-wide Gale Crater. Its main destination was and still is the 5-kilometre-high sedimentary mound, Aeolis Mons, informally called Mount Sharp, which rises from the crater centre; at its base, Aeolis Mons contains clay and sulphate minerals which could have only formed in the presence of water – this made researchers believe that the sediments were once lacustrian.

“If there were lake deposits on Mars, this would be one of the best places to look,” says Dawn Sumner, a Curiosity mission member at the University of California, Davis, who advocated sending the rover to Gale in part because of the possibility that it once contained a lake.

Water and wind


However, a study conducted by Edwin Kite of the California Institute of Technology in Pasadena and his colleagues, published on 26 March, paints a much drier picture of the mountain’s formation. Using images provided by the Mars Reconnaissance Orbiter, he measured the orientation of rock layers exposed at a handful of locations around the mountain’s base. If it was a lake, you’d expect them to be as flat as it gets – but instead, they found that the layers were slightly tilted, by about 3 degrees. This figure, small as it may seem, is consistent with layers being formed by dust blown into the crater by wind.

Of course, if you’re looking for life (as we know it at least), more water is good – so if this is a result of wind and not water, Curiosity could have a problem.

Still, I find it hard to be convinced by the tilt argument alone; even if count out tectonic activity on Mars, there are other phenomena which can account for the tilt. For example, the asteroid that created Gale crater may have also formed a small central mound due to the ground rebounding after impact, which can be responsible for the 3 degrees. Other valid, but not quite as likely phenomena can also account for it.

“There are other ways of explaining why the strata dip away from the mound,” says Gary Kocurek, a Curiosity team member and sedimentologist at the University of Texas at Austin.

Either way, Curiosity will settle the argument once and for all when it finally reaches Mount Sharp.

“We have our desires for what the environment was like on Mars, but the most important thing is that those rocks actually record the history of what happened.”

Nature doi:10.1038/nature.2013.12721

‘Mount Sharp’, the landing site for Curiosity, is just an informal name

I have to admit this one caught me off-guard: Mount Sharp, the destination for the new Mars Rover is at the center of a minor naming confusion: its official name isn’t actually Mount Sharp.

As of today only three days remain until the much expected land, and I was just reading some details about Curiosity and the land itself, when I came across this fact.

“Mount Sharp is only an informal name,” says Guy Webster of NASA’s Jet Propulsion Laboratory, picked in March to honor the late geologist Robert Sharp (1911-2004) by the rover science team. “Bob Sharp was one of the best field geologists this country has ever had,” said Michael Malin of Malin Space Systems, who heads a rover instrument team, in a statement then.

But in May, the International Astronomical Union (IAU) selected “Aeolis Mons” – as part of the long standing tradition to give Latin names to Martian mountains. However, not only the media prefers the “traditional” name – researchers seem to love it too. Even though the IAU named a nearby crater “Sharp”, Webster says, “but the rover isn’t going to visit that one.” No disrespect is intended to the IAU, he adds, “but we’ll probably keep on calling it Mount Sharp.”

So, just so we’re clear, Aeolis Mons and Mount Sharp are the same thing – whenever we’ll make a reference, we’ll try to use both names, but if for any reason we don’t, remember it’s the same thing, with two different names.

As for the Curiosity mission, there’s nothing special going on at the moment. Everything seems to be going according to plan, but researchers are eagerly awaiting for the delicate landing moment. Of course, we’ll keep you posted with everything that happens in these few days, as well as during the land.