Terrestrial snow at Chabot on December 16, 2008
Photo by Craig Coryell

This is quite unusual for the Oakland Hills, of course. In the ten years I've worked here, this is the second, maybe third, dusting I've witnessed. I recall the great freeze of '74, when it actually snowed in Oakland close to sea level—that's the year all the eucalyptus in the hills froze and died.

My mind wandered—pretty far out in space (an occupational hazard at Chabot). I started thinking about all the recent news and discoveries from around the Solar System, my thoughts guided by the fat white flakes drifting down all around the observatory domes.

Last September, NASA's Mars Phoenix Lander detected snow falling high in the atmosphere–about 4 kilometers high. This Martian snow, however, quickly evaporated in Mars' thin, dry air, never reaching the ground. Phoenix used a laser probe to make the detection–so we don't actually have picture to look at!

Snows of the Solar System may also fall out of the plumes of "cryovolcanoes"–the frigid outer Solar System's version of volcanism (may it live long and prosper). On moons such as Saturn's Enceladus and Neptune's Triton, plumes of material have been detected spouting from fissures and cracks–probably fueled by heat generated by tidal forces from their parent planets.

On Enceladus, the geyser plumes contain water vapor and ice crystals, and are believed to come from subsurface lakes of "warm" water (32 degrees Fahrenheit–in other words, ice water… but that's a veritable hot spring, or magma chamber, on a cold moon like Enceladus!).

The ice crystals in the geysers' plumes mostly fall back to Enceladus–maybe in a diffuse fall of "snow" across the globe? I'm waiting for those pictures…

Saturn's large moon Titan is speculated to possibly have a form of cryvolcanism, though no direct detection has yet been made. Still, any water vapor that might erupt from a Titanian cryovolcano might be expected to fall in a form of snow….

Triton, much farther from the Sun than Saturn, is even colder than Enceladus. In fact, it's been called the coldest measured surface in the Solar System, at -391 degrees Fahrenheit. Here, nitrogen freezes solid. Triton cryovolcanoes, or geysers, may be partially solar-heated, but tidal heating within Triton is probably dominant. Triton's geysers spout nitrogen gas and dark material, which falls across the landscape in dark streaks and lighter deposits of frozen nitrogen–a form of extreme cryo-snow, to my imagination!

Now, are you as cold as I am just thinking about it? Time for a cup of cocoa…

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Image: NASA, ESA, P. Kalas, J. Graham, E. Chiang, E. Kite
(University of California, Berkeley), M. Clampin (NASA Goddard
Space Flight Center), M. Fitzgerald (Lawrence Livermore National
Laboratory), and K. Stapelfeldt and J. Krist (NASA Jet Propulsion
Laboratory)

Exoplanets are planets in other solar systems. Though astronomers have detected over 300 exoplanets since 1995, we only have visible-light images of one of them. These photos of the planet Fomalhaut b, taken by the Hubble Space Telescope, have just been published in Science magazine by UC Berkeley astronomer Paul Kalas. The exoplanet Fomalhaut b orbits the star Fomalhaut (pronounced "foam-a-lot"), and at 25 light years away is the closest exoplanet that we know of.

Up until now, astronomers could only detect exoplanets using indirect methods. To learn more about the star wobbles and dips in starlight that indicate other planets are out there, check out QUEST's radio story, Exoplanets, and QUEST's television story, Planet Hunters. These exoplanets are trillions of miles away, but the research happens close to home at the Lick Observatory near San Jose, and at the Chabot Space and Science Center in Oakland.

Over the next few years, astronomers will likely detect additional exoplanets, and will learn much more about them. In 2009, NASA will launch the satellite telescope Kepler, which will be able to detect smallish Earth-sized planets. And in 2013, the James Webb Space Telescope will go into orbit. As stated in this press release, astronomer Paul Kalas hopes the James Webb Space Telescope will tell us whether there are other planets orbiting Fomalhaut – and whether those planets might be able to sustain life. Who knows – maybe on one of those planets, aliens are collecting snapshots of Earth.

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A patch of what might be ice, exposed by Phoenix's
landing rockets.

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.

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Artist concept of a geyser erupting on Enceladus.
Credit: David Seal.

A layer of the veil around Saturn’s moons was removed when Pioneer 11 and Voyagers 1 and 2 made flybys of Saturn in the '70s and '80s. The Saturnian moons, it appeared, were not the lumps of rock and dust that Earth's own Moon is made of, but objects containing no small amount of water ice. Not terribly surprising, considering the low temperatures of the outer solar system where ice-rich comets roam.

Visions of frozen alien landscapes, replete with icicles and ice cliffs and ice fields and ice ice ice! were conjured in my imagination, and in artist depictions of majestic ringed Saturn seen from moons like Rhea or Dione or Enceladus.

Four years ago, Saturn’s first permanent visitor from Earth–the Cassini spacecraft–arrived there, and since has been making extreme closeup examinations of Saturn, its rings, and its increasingly wondrous and beautiful moons. Cassini is almost literally ripping apart veil after veil of our ignorance of these little worlds.

Far from a contingent of enormous but simple snow cone balls, Cassini has shown us that some of Saturn’s moons are apparently alive with liquid motion. First, there were the surface “lakes” and “seas” on Titan, probably made of extremely cold liquid hydrocarbons like methane and ethane–the stuff that spouts out of the gas range in your kitchen. Lakes and seas and rolling waves of liquid natural gas are fine and dandy for an imagined shoreline scene–but take a dip in those "waters" and an actual water-based creature like you would freeze solid in seconds. Scenic, but not inviting for a swim…

But recent observations by Cassini have shown that Titan's frigid unearthly lakes and Enceladus' snowball exterior may just be additional veils that are now being lifted.

In March, Cassini flew within 30 miles of the surface of Enceladus and right through a plume of material venting into space from the moon’s interior—an enormous "geyser." Earlier observations had sensed the presence of water in the plume, giving rise to speculation that liquid water in some form might exist beneath Enceladus' surface—perhaps chambers of liquid heated by tidal stressing of the interior.

When Cassini flew through the plume, its chemical sensors "sniffed" more than just water in the stream, but a good deal of organic molecules as well…not unlike material found in comets, stuff left over from the formation of the Solar System that may have been the building blocks of life on Earth.

The other "water find" was that of a possible liquid ocean under the crust of Titan–similar perhaps to the deep liquid water ocean believed to exist under the surface of Jupiter's moon Europa. Unexpected "drift" in the locations of landmarks on Titan's surface is what suggests a liquid ocean–water with perhaps some ammonia–that the frozen crust may be floating on.

With all the liquid water and organic chemistry being revealed in the Saturn system (and elsewhere in the outer solar system), our imaginations can shift from the older standards of envisioning otherworldly landscapes of sculpted ice or even seascapes of liquid hydrocarbon lapping on shores of water ice sand, to something a little more, shall we say, "lively…"?

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

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