Satisfying Curiosity: preparing for the Mars landing

Artist's depiction of the Curiosity rover on Mars. (Credit: NASA/JPL-Caltech)Unless you are freshly returned from outer space, you have probably already heard about tonight’s eagerly awaited landing of Curiosity, the next Mars rover. By roughly 1:31 a.m. EDT on Monday, the Mars Space Laboratory vehicle will have either delivered the $2.5 billion rover safely to the planet’s surface or dropped it there, broken and maybe dysfunctional. [Update, 1:35 a.m. EDT, Mon.: Success!!!] Either way, Curiosity’s arrival promises to be one of the most dramatic (and media-saturated) science events of the year.

Descent stage of the Mars Science Laboratory vehicle, lowering the folded Curiosity rover in the sky crane maneuver. (Credit: NASA/JPL-Caltech)

Are you ready for it, and for what could the trove of discoveries that the rover may make in the months and years ahead? Here’s a brief backgrounder.

Curiosity’s mission and capabilities

Relative sizes of the tiny Sojourner, Spirit, and big Curiosity rovers. (Credit: NASA/JPL-Caltech)

All the Mars rovers so far, from the trailblazing Sojourner to the overachieving twins Spirit and Opportunity, have been extraordinary exploratory robots, but Curiosity represents an ambitious new extreme. Most obviously, it’s much bigger: Curiosity weighs almost a ton and is the size of a small car, whereas Spirit and Opportunity were half as long and a fifth as massive and Sojourner was not much bigger than a large cat.

Curiosity is also the first to run on nuclear power cells, so it will not be vulnerable to power loss from sand coating solar panels, as its predecessors were. And has often been remarked (usually with frikkin’ allusions to Mike Myers’ Dr. Evil), Curiosity’s instrument package includes a laser for spectroscopy capable of vaporizing rock from a distance of nearly 10 meters. Oh. Yes.

Complementing such analytical tools is an array of cameras, some for navigation, some for scrutinizing the Martian terrain in detail. Alan Boyle at has a thorough and engrossing write-up about their capabilities that I heartily recommend. An excerpt concerning the versatile system of mast-mounted cameras:

Mastcam promises to be the star of the show once the mission hits full stride: The system’s right-eye camera has a telephoto lens, capable of reading the “ONE CENT” lettering on a penny on the ground beside the rover, or distinguishing between a basketball and a football at a distance of seven football fields (roughly 700 yards or meters).

As Boyle explains, the more impressive cameras will not be online until later in the week.

All these instruments are integral to Curiosity’s multiyear mission, which is to examine the geological record in and around the Gale Crater landing site and to thereby illuminate how conditions on Mars have changed over many millions of years. It’s often mistakenly reported that Curiosity is the first rover with explicit capabilities to look for past or present life on Mars (I’ve made that oversimplification myself). If against all odds the rover ran into the Martian equivalent of a fossil sticking out of the soil or lichens growing on a rock, it’s obviously capable of spotting them.

The more accurate description, though, is that Curiosity is designed to help evaluate the historical habitability of Mars — that is, its potential capacity to have supported life during different ages, based on the presence of water, atmosphere, temperature and so on, as reflected in the geochemistry of various strata. If life was actually present during some or all of those times, it might also have left telltale chemical evidence of itself.

Phil Plait of Discover’s Bad Astronomy blog points to an entertaining video from the American Chemical Society that explains more about the chemical tests Curiosity will run during its trek. I can also recommend these articles from The Guardian and The Atlantic, by Stuart Clark and Ross Andersen respectively, for great overviews of Curiosity’s mission.

The wild “sky crane” landing scheme

Spaceflight engineers consider the atmospheric entry, descent, and landing phase of any planetary exploration to be the most perilous because it is when total, mission-scrubbing failure is easiest and maybe most likely. In the case of Mars, failures have been particularly numerous. NASA’s widely seen “Seven Minutes of Terror” video vividly dramatizes the challenges that the Mars Science Laboratory will face as it tries to execute a unique “sky crane” maneuver for placing Curiosity on the surface.

Credit: NASA/JPL

In short, within just seven minutes, the Mars Science Laboratory needs to slow from 13,000 miles an hour down to almost zero while landing within a small elliptical target area just 20 kilometers long and seven wide near the base of a mountain. To do so, it will steer its way through the outer atmosphere (which is itself unprecedented), deploy a parachute to further reduce speed, then launch a thruster-powered descent platform that will fly to within 20 meters of the ground, then slowly lower the rover on tethers that blast loose when no longer needed so that the sky crane platform can fly away. Moreover, it must do all of this entirely on its own, without any live human guidance or intervention, because the 14-minute radio delay imposed by the distance between Mars and Earth means that Curiosity will be on the surface minutes before scientists in mission control hear that the spacecraft has entered the atmosphere.

A month ago I wrote about the sky crane in some detail for my column at

Why Gale Crater?

Representation of Aeolis Mons in Gale Crater, showing the small ellipse where the Mars Science Laboratory aims to land. (Credit: NASA/JPL-Caltech)

A number of landing sites were considered for Curiosity, but the one that won out was Gale Crater because of its seeming likelihood to offer good answers about Mars’s geohistory. (It had been a contender as a landing site for the Spirit rover, too.) The crater, 154 km. wide and on average about 5 km. deep, probably formed from an impact more than 3.5 billion years ago, when Earth’s continental plates were still just beginning to cool. At the center of the crater is a mountain, Aeolis Mons (sometimes called Mount Sharp) as high as the crater is deep.

Aeolis Mons is what makes Gale Crater so interesting, which is why Curiosity is set to touch down so close to its base. Images from orbiting probes suggest that the mountain is a stratified mass that was shaped by water: either the crater was once filled with water and the mountains sediments accumulated over time or the crater was filled with rock and water gradually wore away the rest, much like how the Grand Canyon formed. But Aeolis Mons is twice as high as the Grand Canyon is deep.

As notes:

Scientists have been studying those layers using images from the HiRISE camera on MRO have discovered that clays in Gale Crater can only be found lower down in the crater. Which is to say that these layers are older than the sulfates, deposited by salty water.

Clays are only seen where water is abundant and the sulfates tell us that Gale Crater went through a period when water evaporated away.

What the floor of Gale Crater appears to be telling us is that standing water, at least locally, existed long ago on Mars, but later evaporated away. This is consistent with what we have seen in other parts of Mars, of course. Ever since the rovers landed on Mars we’ve seen one piece of evidence after another of standing water or even of running water in the Red Planet’s distant past.

Nancy Atkinson of has more on the landing site, including some great images of it. If anyplace can tell us whether conditions on Mars might have supported life at one time, it’s likely to be Gale Crater.

Where to follow the action

Space Industry News has compiled a list of places online and here in meat space where you can follow the coverage of Curiosity’s landing — including your Xbox360, if you’re so inclined. That latter seems only fitting, given that NASA has also created an interactive online simulator that allows you to try your hand at landing Curiosity. Phil Plait will also be participating in a live video Hangout on Google during the event.

You could also follow it on Twitter through the @MarsCuriosity account or the #MSL hashtag. The rover also has its own Facebook page.

And if you’re in New York, you can watch NASA’s coverage live in Times Square on the Toshiba Jumbotron. (I don’t expect the crowds to be quite of New Year’s Eve caliber.)

Rein in your expectations of what you’ll see during any of this live coverage, however. Remember, Curiosity’s most beautiful cameras don’t come online for several days, so most of what will be shown will be telemetry information, simulations, and possibly images sent back from the orbiting Mars Reconnaissance Observer spacecraft, which should be able to train its glorious HiRISE telescope on the lander during the deployment of its parachute.

Courtesy of the European Space Agency, here’s a timetable for the landing:


  • CEST = UTC + 2 hours
  • Earth time = Mars time + 13min:48sec
  • MEX: Mars Express
  • MSL: Mars Science Laboratory
  • NNO: ESA New Norcia station
  • AOS: Acquisition of signal
  • S/C: Spacecraft


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    [Well… no. Sorry. I could indulge the goofy fun of letting you spread conspiratorial nonsense, but it feels a little beneath the dignity of PLOS Blogs, so no. —The Editroid]

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