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….

NASA’s MESSENGER spacecraft at Mercury-artist concept.

Photo by: NASA

I’ve been waiting for the “whole story” on Martian ice at the Phoenix lander site to unfold more completely, but the chemical analyses have not yet run their full courses-so I’ve decided to widen the focus on this blog to give a status report on current active robotic exploration of planets going on around the Solar System.

Limiting my scope to only planetary spacecraft, the list is still respectable. In no particular order, here’s the round-up:

Spirit: Mars Exploration Rover Spirit’s activities on the Martian surface have been reduced to save on power, but the robot remains alive. With the arrival of Martian winter, Spirit spends more power running heaters to keep key electronic and power equipment healthy. Spirit remains in the giant Gusev Crater, where it will spend its entire life on Mars.

Opportunity: Exploring a much smaller crater of its own, Victoria Crater-Spirit’s twin, Opportunity, continues its investigation of the rock layers of Mars’ geological history. As of June 10, Opportunity has clocked in at 7.26 miles of total “roving” on Mars, since its landing back in 2004.

Phoenix: The brand-spankin’-new Mars Phoenix lander has been digging into one of Mars’ greatest scientific mysteries: water. Detailed chemical analysis of samples taken at Phoenix’s site near the northern polar ice cap is underway, but the big question– is Phoenix standing on frozen Martian water– has been answered: yes.

Mars Reconnaissance Orbiter: The newest orbiter in the Martian fleet continues to send back its extreme-high-resolution imagery and its revealing chemical measurements, as well as to serve as a high-speed data and communication relay for other Mars-exploring robots.

Mars 2001 Odyssey: Credited with detecting the massive amounts of frozen water in Mars’ northern hemisphere-the same ice that the Phoenix lander is now scraping at, Mars 2001 Odyssey continues its surveillance of Mars’ chemistry and atmosphere.

Mars Express: The European orbiter that launched the ill-fated Beagle II lander has continued on a respectable career of exploration in its own right. Mars Express also helped support the landing of the Phoenix.

Cassini: Saturn’s first robot-in-residence, Cassini, has concluded its initial 4-year mission and is now continuing on an extended mission. Cassini has given us unprecedented close-up images and measurements of many of Saturn’s stunning moons, its complicated ring system, and the swirling, aurora-touched cloud formations of Saturn itself.

MESSENGER: The first spacecraft to visit the little-understood Mercury since 1975 made its first flyby of that planet last January, and will settle into a permanent orbit in March 2011. Even the few pics it snapped as it hurled by gave us far more detailed images of Mercury than ever before.

New Horizons: Launched a couple years ago on its outward bound, meteoric flight to Pluto, New Horizons has already performed some exploration duty, capturing images and data of Jupiter, Jupiter’s volcanic moon Io, and Jupiter’s long magnetic “tail.” Now in “cruise mode,” this little robot will fly past Pluto (dwarf planet; king of the Plutoids) in July 2015.

Voyagers 1 and 2: Do you remember the remarkable voyages of discovery made by the Voyager spacecraft, both launched in 1977? Since completing their primary missions of flying by the Gas Giant planets (Voyager 1 at Jupiter and Saturn, Voyager 2 at all four), these two veterans have continued to operate and send information back to Earth, and are now about 3 times more distant from the Sun than Pluto.

That’s the wrap. If I missed anyone, my apologies!