Gale Crater, the destination for NASA's new rover Curiosity. Credit: NASA, Google Earth

Ready for yet another great Martian adventure? Another prestigious interplanetary mission to that fabled world? The next technological ambassadorship of space-age robots and exotic landscapes? Or, how about an inglorious romp to go dumpster diving to sift through a pile of geological garbage…?

In any case, get set; on November 25th the launch window opens for NASA’s next Mars rover, “Curiosity,” which will arrive over yonder next August.

Inglorious dumpster diving? What’s NASA got planned this time, anyway?

Answer: Gale Crater, a large impact blast about 1400 miles to the west of Gusev Crater, where the rover Spirit now sits motionless—and incommunicado—in its last rusting place.

When I heard that Curiosity was bound for Gale Crater, my first impulse was to start up Google Earth, switch to Mars mode, and zoom in on Gale Crater for a landing to see, at least superficially, what might be of interest there to an explorer. (You can do this too; download Google Earth at www.google.com/earth, select Mars, and search for Gale Crater.)

My first Google-vista of Gale, which included several overlaid strips of high-resolution imagery from the Mars Reconnaissance Orbiter (MRO), hinted that there may be a LOT of interest here.

Gale Crater, about 90 miles across, sports a really large mountain right in the middle—mostly filling the bowl, in fact. The mountain, whose peak rises around 2700 feet above average Martian surface level (can’t say sea level there…not in the present day, at least), towers 3 miles above the deepest part of the crater surrounding it.

I zoomed in on an MRO overlay of a canyon high on the mountain, finding what looks like layered deposits exposed by whatever cutting action had carved the canyon in the past. The landscape I find there is stunning, the details rich. I almost feel as though I’ve stood where Curiosity is soon to tread.

The rover will be set down by a sort of rocket-propelled winch, lowered gently to the base of the mountain where an alluvial fan promises potential riches. Not wind-worn pebbles of solid gold, not fist-sized chunks of diamond—well, probably not—but rather the riches of dirt that may have been deposited there by the action of water. A dumpster of chemical, geological, and potentially biological history.

One of the reasons Gale Crater was chosen as Curiosity’s destination is that it is a deep, low-altitude impact crater, situated at a “downhill” destination where water, if indeed it did flow on Mars long ago, is very likely to have converged, dumping all sorts of soil, rock, and whatever else might have come along for the ride.

Curiosity carries ten instruments designed to conduct a range of measurements, including chemical analysis of soil and rock samples in search of organic compounds that may have been preserved. Where Curiosity’s predecessors, Spirit and Opportunity, have looked for the chemical signs of past water to help tell us whether Mars was ever hospital to life, Curiosity will look for the leftovers of life itself. And in the bottom-lands of Gale Crater, at the foot of a huge mountain from which the rubble of layer upon layer of history has been scoured, it will be in a really good place to do it.

Endeavour Crater; Credit: NASA, Google Earth

Who would have imagined three years ago, when the already veteran Opportunity set forth from its two-year prospecting site at Victoria Crater on a long march to the much larger Endeavour Crater, that the Fates would actually NOT stop this Energizer-Bunny dead in its tracks?

Okay, enough jaw-dropping incredulity. Some things CAN be built to last….

About three weeks ago, Opportunity reached the rim of the 14-mile wide Endeavour Crater, after clocking nearly 21 miles since its landing seven and a half years ago. By Earth-rover standards, that’s about one round trip to work and home again for me, and about 25 minutes of my time—but Opportunity’s commute is a far greater feat, alone on another world, long minutes away even by radio waves, no service garages for maintenance, no fuel stations other than the daily dose of energy doled out by the Sun.

One of the first things Opportunity did upon reaching the rim of the giant crater, after taking some pictures to give us the lay of the land, was to examine some rocks. After all, more than anything else, the Mars Exploration Rovers are geologists, or rock hounds, sent to tell us about the Martian environment, today and in the past, through the chemical makeup and stratigraphy of the rocks and soil.

Data from orbital spacecraft have shown that the materials at the rim of Endeavour may date back to early in Martian history, making for fertile ground in Opportunity’s quest to uncover clues to the planet’s past. Evidence for the presence of clay minerals, possibly formed under wet conditions favorable to life, has been brought to light—which really adds some excitement to the rover’s rock hounding exploits to come.

On Opportunity’s approach to the crater rim, it spotted in the distance unusual outcroppings, and a “shelf” of what looks like sedimentary rock with inclusions of material that may have been deposited by water action.

Water water water, the watch-words of Martian exploration for many years. Where there is, or was, water, perhaps there is, or was, some form of life. And while the Mars Exploration Rovers weren’t designed to look for signs of life directly, their larger, better equipped descendant, Curiosity, to be launched in November, is. Curiosity, do tell….

As a child I liked to imagine what it would be like to land on and walk about the surface of Mars. Mind you, back then we had no images from Mars’ surface—not until 1976 when Viking landed. We had low-res images taken from space, and plenty of science fiction sound stage backdrops and sets from various TV shows and films (and a Mars stand-in, Death Valley, in Robinson Crusoe on Mars).

Opportunity still appears to be in good shape, so the odyssey of its exploration seems to have a good chance of delivering yet another episode of the Life (?) and Times of Mars….

Gullies in wall of Hale Crater. Credit: NASA/MRO

Here's a quick status on the active ones:

Mars Reconnaissance Orbiter: The most recent arrival at Mars (2006), MRO's 5-year mission (hmmm—sound vaguely familiar?) is to study the history of water and climate on Mars, as well as to serve as a telecommunications relay for other spacecraft. Armed with a suite of powerful instruments to study the atmosphere, surface, and subsurface of Mars—including a camera, HiRISE, that can almost read the license plates on Martian automobiles—MRO has to date sent back more data than all other Mars missions combined. It's not been a glitchless flight, however: in 2009, MRO's computer reset itself four times for unknown reasons; the last reset, in August, was followed by a 4-month operational hiatus as Earth-side controllers performed some careful programming updates to help guard against effects of any future resets. MRO resumed operation in December.

Mars Odyssey 2001: NASA's 2001 Odyssey is still going fine after nine years—although the computer glitchiness out around Mars seems to be catching: Odyssey's computer put itself into a safe mode last November 2009 in response to a memory error. This was corrected and Odyssey has resumed doing science. Among Odyssey's major discoveries was the detection of huge expanses of water ice just under the surface of polar lowlands, and the surveying of deposits of water-related minerals in various locations around the planet.

Mars Express: Arriving at Mars in 2004, Mars Express became the European Space Agency's first mission to another planet, which was recently extended to 2012. Though the Beagle 2 lander component of the mission fell to Mars and was never heard from again, the Mars Express orbiter has sent back years of captivating images and important data, including the confirmation of methane in Mars' atmosphere (whose source is in all likelihood subsurface, and the origin of which—organic or inorganic processes—is being debated).

Mars Exploration Rover Opportunity: After six years of crawling around Meridiani Planum discovering chemical and geological evidence for past water on Mars, Opportunity is now on a long march to a large impact crater, which it will reach (if it can keep on running) in about two years. Currently, the rover has stopped to RAT out chemical and geological information from a rock called Marquette Island—the RAT is its rock abrasion tool, or rock grinder. Still going….

Mars Exploration Rover Spirit: Also still alive after six years—almost 25 times longer than it was planned to run—Spirit has been stuck in a sand bog for the last six months. With a couple of wheels on the fritz, Earth-side operators have been confounded in trying to free the robot—but Spirit has continued to make scientific measurements anyway…and in fact made a significant discovery in the course of trying to get unstuck.

Phoenix lander: Although it's been in the deep dark freeze of a Martian winter since November 2008, the Phoenix lander has an outside chance of survival. Now that light is returning to Phoenix's landing site, NASA is listening for the robot's radio signal, in case the return of solar power means that Phoenix will rise from the frost and live again! So far, no such signal….

Next up: The Mars Science Laboratory rover, "Curiosity."

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Block Island—a half-ton meteorite found on Mars by NASA's
Opportunity rover.Image credit, NASA/MER Opportunity

Okay, dramatic desert car scene ended. That would be the Hollywood movie version of what NASA's Mars Exploration Rover Opportunity did recently, on the lonely desert highway that it's scouting on Mars.

On its determined long trek from Victoria Crater to the larger Endeavour Crater (a 12-mile span that Opportunity has completed about one fifth of over the past year), the rover passed by an X-box-sized block of iron that presented the appearance of a meteorite. It snapped a picture in passing, which was eventually transmitted to Earth and examined. By this time, Opportunity had already traveled about 180 meters beyond the block (dubbed "Block Island"). This is when the rover was commanded to backtrack all the way to the find (though it's doubtful it worked up a rooster tail).

Upon returning to Block Island—quite obviously an iron-nickel meteorite by appearance alone, but whose composition was confirmed by the rover's alpha particle X-ray spectrometer instrument—Opportunity took more pictures, including extreme close-ups with its microscope camera, which revealed surface patterns similar to those found on Earth iron-nickel meteorites that have been exposed to long-term weathering by wind and sand.

As interesting as stumbling upon a half-ton meteorite on the dusty plains of Mars' Meridiani Planum is, what this particular chunk of weathered iron is telling scientists sparks the imagination. In a nutshell, given the thinness of Mars' current atmosphere, scientists wouldn't expect a meteorite of this size to survive impact intact, at the speed it would be going. One of the possible explanations for Block Island's rock-houndable state is that when it fell to Mars, Mars' atmosphere was substantially thicker than it is now.

Further examination of the meteorite may reveal clues as to how long ago it fell through Martian skies. Evidence that Mars' atmosphere was warmer and thicker in the distant past, as well as the possibility that there was liquid water on the surface, has been mounting over the years. The age of this meteorite-fall could shed more light on the history of Mars' environment. If it fell billions of years ago, Block Island would weigh in as more evidence to support our current suspicions. If, however, we find that it fell more recently, then this could indicate that the atmosphere was more substantial later in Mars' history than we thought.

Imagine, if you will, a Mars that looks even more Earthlike than it does now: seas of water with waves rolling into shorelines, great clouds sending downpours of rain and snow onto mountains and plains, streams and rivers snaking through the landscape. Maybe, maybe, even some form of life?

All that from a rock? Yes, rocks talk, if we listen.

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The Eye in the Sea. Credit: MBARI.

The Eye in the Sea is one of the coolest, gee-whiz scientific projects you'll see. It's part of the Monterey Bay Aquarium Research Institute's so-called MARS project (that stands for Monterey Accelerated Research System). MARS is an undersea laboratory, set up deep on the sea floor about 30 miles offshore from Monterey.

The Eye in the Sea is one of the first research projects to be hooked up to MARS. It uses a small amount of red light to view what’s happening on the ocean floor, about 3,000 feet below the surface. The images travel through 32 miles of cable and go back to the control center on land, where researchers view real-time video of life at the "benthic" level – that is, a voyage to the bottom of the sea.

And you're going to be able to take that voyage, too.

Schoolchildren, teachers and eventually the general public will be able to see the spindly-legged crabs calle spiny kings, or the eel-like hagfish, or the giant, dark, blob-like Pacific sleeper shark.

The Eye in the Sea becomes operational in January, and researchers expect to have their school program up and running by late January or early February, depending on the success they have hooking up Eye in the Sea to the metal hub out in the middle of Monterey Bay.

All of that means that the public will be able to go to www.mbari.org beginning sometime in February and view video-cam images from half a mile deep on the sea floor.

How cool is that?

Watch video from the Eye of the Sea in the Underwater Laboratory audio slide show online.

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Picture of the edge of Victoria Crater superimposed with
image of the rover Opportunity.
Credit: NASA/JPL

Mars reaches "opposition" on December 24th. This is the time when Earth crosses directly between the Sun and Mars–in other words, when Mars is at the opposite end of the sky from the Sun and at its closest distance from Earth–this time about 55 million miles. You can see Mars yourself in the evening hours if you face east and look high: it's that steady, bright, orange dot right between Gemini and Taurus.

So what's been happening on Mars, exploration-wise? Here's a quick summary on that score:

NASA's Mars Exploration Rovers, Spirit and Opportunity, have had their tours of duty extended a fifth time, which should keep the rovers going–their health willing–possibly through 2009. Having landed on Mars in January of 2004 for a nominal 90 day mission, the robot pair has now lasted almost four years.

Spirit, which landed in the huge Gusev Crater, has traveled four and a half miles from its landing point and is now exploring a range of hills on a volcanic plateau. Probably topping the list of scientific evidence it has turned up is that water, in some form, has altered the chemistry in the environment, sometime in the past.

Opportunity, on the opposite side of the planet from Spirit, is currently exploring the half-mile-wide Victoria Crater. Exposed rock layers in the walls of the crater are expected to be an excellent "book" of Mars' geologic history for Opportunity's various instruments to read.

In its more than seven mile journey, Opportunity has revealed even stronger evidence that Mars' distant past may have been warmer and wetter, and that, at least in Opportunity's neck of the woods (Meridiani Planum), there may have been extended periods with liquid surface water.

The Mars Reconnaissance Orbiter spacecraft, with its array of instruments and super-powerful camera, has produced the most discerning orbital imagery of Mars' surface to date, giving us aerial views of the Martian deserts, canyons, ice caps, plateaus, volcanoes, craters, drainage channels, sand dunes, and so on, that look like they could have been taken from the window of a small airplane flying at very low altitude.

Even as Spirit and Opportunity send back postcard after postcard from the ground, like a pair of camera-happy tourists, that tantalize us with evidence of possible lakes, seas, and oceans in Mars' past, Mars Reconnaissance Orbiter with its more global viewpoint has revealed evidence that suggest another possibility: that the apparently periodic "bursts" of water activity might have been the work of large meteoroid impacts blasting through layers of ice and creating temporary episodes of water melt…

To round out the role-call, NASA's 2001 Mars Odyssey and Europe's Mars Express orbiters are also still in business and contributing to our already huge–but nowhere near complete–body of knowledge of that wandering orange dot in the sky…

Benjamin Burress is a staff astronomer at The Chabot Space & Science Center in Oakland, CA.

latitude: 37.8148, longitude: -122.178

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