Artist concept of the Phoenix lander,
sleeping under the darkening polar skies of Martian autumn.It seems like only last month that we witnessed the drama of NASA's Phoenix landing on Mars. We were on the edge of our seats in Chabot's planetarium during those "seven minutes of terror" as Phoenix burned a meteoric path through Mars' atmosphere.

But that was last May, and Phoenix has operated near Mars' northern polar ice cap going on six months now! The mission has continued a couple months longer than originally planned, giving Phoenix more time to dig in the icy soil, bake scooped up samples to detect what chemicals sublimate, track the polar weather day and night, and look to the skies with its various instruments.

Phoenix sent back some very interesting news. Indeed, it had landed on what turned out to be dust-coated water ice; ice that contains chemicals like calcite and perchlorate– the former of which may indicate past liquid water on Mars, the latter of which, however, is generally toxic, and may complicate arguments for life, past or present, on Mars.

One of the more "fanciful" detections by Phoenix was falling snow: two or three miles above, Phoenix detected ice crystals falling from clouds– albeit flakes that never made it to the ground, instead evaporating like Earthly virga back into the atmosphere.

But Phoenix’s mission has a built-in conclusion (unlike the seemingly perpetual Energizer Bunnies exploring the Martian tropics, aka the Mars Exploration Rovers). Phoenix landed at 68 degrees north latitude– that’s equivalent on Earth to the north coast of Alaska, Norway, or south central Greenland– prior to Martian northern summer solstice (which was June 25). As with Earthly summertime, the polar days were unending, the Sun above the horizon 24 hours a day (yes, Mars' day is about 24 hours long, just as on Earth). This provided Phoenix with its electrical power, generated by photovoltaic panels.

But now the Sun is dipping below the horizon several hours a day as the Martian northern hemisphere slides in the direction of autumnal equinox (December 26, 2008), at which time the Sun will spend half the time below the horizon, the other half never rising very high. Already, Phoenix's solar panels are generating considerably less power than in the heyday of its mission. A dust storm, filling the air and blocking some of the already weak sunlight, has also cut available power to the lander for a time in October.

The diminishing conditions also caused Phoenix to put itself into an automatic "sleep" mode in late October, waking up for only a short time each day, when solar energy was at a peak. To give a flavor of the temperatures Phoenix is enduring, on Sol 151 (the 151^st Martian day since landing-October 27^th, Earth time), the daily high reached a balmy 50.8 degrees F-negative 50.8 that is! The night time low hit -128 degrees F… .

With every day possibly being the last we hear from Phoenix, scientists are collecting as much data as possible, mostly focusing on meteorological conditions. Reporting from the Martian polar ice cap, as the icy darkness of winter begins to settle in, this is Phoenix Lander, signing off….

The ‘Snow White' excavation trench, after rasping
and digging by Phoenix. Credit: "NASA/Mars Phoenix"

Since witnessing the historic landing of NASA's Mars Phoenix Lander on May 25, I've been holding my breath to learn if Phoenix has made the discovery it set out to make: whether it landed on a vast deposit of water ice near Mars' northern polar cap.

It took several weeks after landing for the declaration to finally be made-and without further ado, YES, definitely, water ice was found by Phoenix. But even now, in August, it seems the declaration of Phoenix's great discovery is still in the process of unfolding, one careful and tantalizing announcement after another.

From a lay point of view one might think, why did it take weeks for Phoenix scientists to announce that, yes, the white stuff scraped up by the lander's instruments, from under a thin topping of soil, is water ice? And why do there seem to be unanswered questions about the nature of that ice even now, three months after landing?

For those familiar with how a remote robot probe like Phoenix makes its investigation, this is not surprising at all. In fact, serious scientific measurements by Phoenix didn't happen immediately after landing. The mission team had a lot of work to do to make sure the spacecraft was healthy and undamaged, ready to explore.

Then, the team worked Phoenix's robot arm and soil scooper to dig, scrape, and eventually scoop up soil and bits of the white substance and drop it into Phoenix's onboard laboratory compartments. At first, there wasn't much of the white substance included in the scooped up samples. Then, the sample stuck to the scoop. So, just getting an adequate sample into the spacecraft where it could be analyzed wasn't a simple matter of scoop and dump….

Eventually, though, the white substance was identified as water ice. The first clue came when the white substance was exposed to the air and sunlight after being dug up, when it began to slowly disappear: it sublimated (went directly from its solid state to a gaseous state, without passing through a liquid state, without passing Go and collecting $200…). If the white substance were, say, a type of salt, it wouldn't have done that.

Inside Phoenix's chemical laboratories, more definitive tests were performed. One instrument is essentially a small oven in which a sample is slowly heated and any gases that boil off (excuse me: sublimate) are identified by a gas analyzer.

But there were still plot complications! One is the possible detection of the chemical "perchlorate" in the ice sample: an oxidizing ion (a compound of chlorine and oxygen) which, if it does turn out to exist in the Martian ice, will give scientists new food for thought on Martian chemistry and the implications for possible Martian life. It wouldn't rule out the possibility of life (past or present), but is an additional factor in the equation.

So, the search for life on Mars-the big-picture-reason we've been looking for water there-goes on. We have to keep in view the fact that finding microbial life, or fossils thereof, on Mars isn't as simple a matter as snapping a picture and looking for plants and animals; it's more like a 19^th Century story I heard of where a race of mile-high beings from Jupiter land on Earth, and at first don't realize there is life here, under their feet….

A patch of what might be ice, exposed by Phoenix's
landing rockets.So, did it land on ice? Huh? Did it?

Two blogs ago I wrote about the then upcoming landing of the Phoenix spacecraft on Mars, near the Northern polar ice cap (Probing the Martian Pole). The entire point of landing on Mars' extreme northern plains was to find and examine ice-ice we know is up there in great abundance, as detected by orbiting spacecraft (Mars Odyssey 2001).

There, frozen under the surface dust layers, is a vast deposit of ice-"enough to fill Lake Michigan twice." So Phoenix was sent to actually land there and scrape up surface samples of the soil, and hopefully ice. The question was, would the layer of dust covering the ice be thin enough for Phoenix to reach the ice with its robotic arm and shovel?

The landing occurred on May 25th-a successful landing. NASA broadcast the drama live on NASA TV, which we shared with several hundred Chabot visitors via planetarium, theater, and closed-circuit TV. There were no actual images coming from Phoenix during the landing-after all, it was cooped up in its protective shell for much of the descent-but the excitement of the real-time drama and the nervous faces of NASA/JPL were enough to enthrall our audience. Pictures wouldn't come form Phoenix until later that night at the earliest.

But the pictures did come in over the days following. At first they looked much like images from other Mars landers (Viking, Pathfinder, Spirit, Opportunity), only flatter. Rusty red soil, low flat horizon, a scattering of pebbles and rocks. The landscape itself appeared less interesting to me than other landing sites-but if you measure Phoenix's success by the beauty of the scenery, you're missing the point.

Phoenix is pretty much all about the ice, and what chemicals are frozen and preserved in it. The questions asked by the Phoenix mission are: did life ever arise on Mars, is the current climate on Mars suitable to support life, and what is Mars' geological makeup? If the vast ice deposits of the flat northern hemisphere lowlands are the frozen leftovers of what was once a liquid sea, then are there chemical clues of past conditions-even past life-locked up and preserved there?

So, do we have answers to these questions yet? Is there ice under Phoenix within reach of its scooper? At the time of my writing this the answer is: maybe. During the first week of testing Phoenix's systems to get it ready for full-on prospecting, a picture of the ground underneath the lander was taken using the camera attached to the robotic arm. This picture revealed a patch of solid substance that seems to have been exposed by the blast of Phoenix's landing rockets. It looks like it could be ice, but until a sample is analyzed we won't know for sure (because, it could be solid rock, too).

The first sample scoop of soil dug up by Phoenix's shovel was placed in a bucket on board the lander and examined by camera, before being carefully dumped into a designated sample waste location (Mars' first land fill). The picture revealed some white substance in the reddish soil-which could be ice, or possible salt.…

Stay tuned in the coming days and weeks for hot news from the ice as Phoenix conducts its investigations in earnest.

Mockup of Phoenix (top) and 'Robinson Crusoe on Mars'
(bottom)—both set in Death Valley National Park…
Credit: NASA (top), Paramount Pictures (bottom)It's that time of the Martian year again: when a flying saucer from Earth appears in the skies of Mars. Imagine if there actually were Martians up there: what's science fiction here on Earth would pass for reality on the Red Planet—and a routine occurrence at that!

This time the flavor of the day is the Phoenix Lander, courtesy of NASA, scheduled to land on May 25th at about 4:38 PM PDT. We'll be watching live NASA coverage of the landing at Chabot Space & Science Center that afternoon, if you'd care to join us…

Following somewhat in the footsteps of the Viking landers of the 1970s, Phoenix's primary mission is to look for evidence of life, or at least the chemical conditions that might be suitable for life to exist. The two Viking landers carried small chemical laboratories that analyzed soil samples scooped up from the surface, as does Phoenix.

While its mission parallels that of Viking, one big difference from Phoenix is its destination: the Northern Polar Ice Cap of Mars. The Vikings landed much farther south in the mid latitudes. Phoenix is targeting the ices of Mars' arctic region.

Growing up, one of my favorite sci-fi films was Robinson Crusoe on Mars. Made in 1964, the same year that Mariner 4, the first space probe to Mars, was launched, RCOM made a descent stab at imagining what it was like. So what if the main character walked around in apparent t-shirt weather and with sufficient atmospheric pressure to keep his blood from boilin–he still wore a respirator that doled out oxygen from an ever-dwindling supply tank, a nod to Mars' thin atmosphere.

A couple of other things our astronaut Robinson Crusoe found on that fictional Mars that we are now looking for on the real one: liquid water and life…Our hero found small caches of water (with the help of a monkey) in grottos between the rocks, and, lo and behold, living in that water was a vine-like life form with edible fruit or tubers. He even took a foot-trek, along with his guy Friday, to the polar ice cap…

(I also loved the film because some of its "Martian terrain" scenes were shot in my favorite spot on Earth, Death Valley…)

Though evidence of past liquid water action seems to be all about the planet, Phoenix certainly won't find any brooks or pools or grottos of spring water, owing at least in part to the frigid arctic region it will set feet on–an arctic zone on a world where the warmest temperatures in the tropics might reach levels of the coldest climates on Earth. What's important about landing on Mars' ice cap is that Phoenix is almost certain to dig up some water–albeit frozen.

And it is the chemical compounds either locked up in that ice or preserved by its proximity that Phoenix is interested in. (Similarly, climatologists on Earth study ice cores from Antarctica to analyze the trapped and preserved gases of Earth's atmosphere of past millennia.)

We wish Phoenix a happy landing, and look forward to the first images and discoveries from the Martian North Pole. And I'm fairly confident the epic polar adventure ahead won't resemble in the least another "great" film of 1964: Santa Claus Conquers the Martians….

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