A library for Mars

by Alan Boyle
The Phoenix Mars Lander is equipped with instruments that could detect the signature of life on Mars - but it also carries signatures, stories and lots more for future generations. The nonprofit Planetary Society is sending along what's billed as the first library for the Red Planet: a silica-glass mini-DVD encoded with scores of stories about space exploration, audio and artwork from some of our planet's best and brightest, plus digitally encoded names submitted by thousands of Earthlings. Perhaps the coolest thing about the DVD is the label addressed to future visitors on Mars: "Attention Astronauts: Take This With You."It's not out of the question that some Marswalker will actually pick up and decipher that DVD someday: After all, one of the places moonwalkers have visited is the landing site for the Surveyor 3 probe, which touched down in 1966 and happened to be within walking distance of the Apollo 12 lunar module three years later.

Unfortunately, it will take humans much more than three years to get to Phoenix's intended landing site in Mars' northern highlands. Fortunately, the Planetary Society's DVD is built to last at least 500 years, and perhaps much, much longer.

What would a Martian traveler find on the disk? Assuming that he or she could figure out how to decode the DVD, the "library" would yield 80 forward-looking stories and articles - including literary classics penned by Voltaire and Jonathan Swift, science-fiction classics by Arthur C. Clarke and Kim Stanley Robinson, and many more goodies well worth adding to your reading list. Of course you'll find Orson Welles' radio retelling of "The War of the Worlds," as well as Mars-themed sci-fi art and photos of the real Mars, as seen by past space probes.

The DVD also includes audio-enhanced slideshows in which Clarke and other luminaries (including the late Carl Sagan) speak directly to future Martians. For Sagan's audio clip, go to this Web page and click on the link titled "Hear Carl Sagan's Message to the Future."

These presentations, along with many of the text/video/audio selections, were first placed on a CD-ROM titled "Visions of Mars" more than a decade ago. In an exercise much like the current project, the CD-ROM was placed on Russia's Mars 96 probe. That spacecraft, however, never got out of Earth orbit due to the failure of a booster stage. The first Martian library went down in flames, and the Planetary Society had to start from scratch.

"We were looking for several years for another ride, essentially," the Planetary Society's Susan Lendroth explained. The team behind Phoenix Mars Lander obliged, and so "Visions of Mars" project director Jon Lomberg updated the content for a fresh launch.

Meanwhile, the society put out a call for people to submit their names for digital inclusion on the disk - following up on similar "send-your-name-to-space" projects for the Mars Exploration Rovers, Selene, Stardust, and so on. About 250,000 people answered the call (including yours truly).

Bruce Betts, director of projects for the Planetary Society, said the resulting mini-DVD is made of material that should last even though it's sitting on the exposed part of the spacecraft, in full view of Martian passers-by. That's the whole point, said the society's executive director, Louis Friedman.

"Since the Planetary Society's disk should last for centuries on Mars, we hope astronauts at some future date will enjoy the visionary works we have sent in this first Martian library," Friedman said in a news release. "These tales and images have inspired generations about the wonder of space, including many men and women who are now researchers and engineers in the space program."

What would you put on a digital disk destined for another world? Are there obvious choices that Friedman, Lomberg and the other folks behind "Visions of Mars" have missed? One audio expert has wondered whether "Visions of Mars" would be playable even a few decades from now, let alone hundreds of years - and that's an interesting point. Do you have any better ideas for preserving interplanetary time capsules? Feel free to leave your suggestions as comments below.

Mars rover finds "puddles" on the planet's surface

The report identifies specific spots that appear to have contained liquid water two years ago, when Opportunity was exploring a crater called Endurance. It is a highly controversial claim, as many scientists believe that liquid water cannot exist on the surface of Mars today because of the planet’s thin atmosphere.

A new analysis of pictures taken by the exploration rover Opportunity reveals what appear to be small ponds of liquid water on the surface of Mars.

If confirmed, the existence of such ponds would significantly boost the odds that living organisms could survive on or near the surface of Mars, says physicist Ron Levin, the report's lead author, who works in advanced image processing at the aerospace company Lockheed Martin in Arizona.

Along with fellow Lockheed engineer Daniel Lyddy, Levin used images from the Jet Propulsion Laboratory's website. The resulting stereoscopic reconstructions, made from paired images from the Opportunity rover's twin cameras, show bluish features that look perfectly flat. The surfaces are so smooth that the computer could not find any surface details within those areas to match up between the two images.

The imaging shows that the areas occupy the lowest parts of the terrain. They also appear transparent: some features, which Levin says may be submerged rocks or pebbles, can be seen below the plane of the smooth surface.

Speedy evaporation?

Levin and other reasearchers, including JPL's Michael Hecht, have published calculations showing the possibility of "micro-environments" where water could linger, but the idea remains controversial.

“The temperatures get plenty warm enough, but the Mars atmosphere is essentially a vacuum," says Phil Christensen of Arizona State University, developer of the Mars rovers' mini-Thermal Emission Spectrometers. That means any water or ice exposed on the surface evaporates or sublimes away almost instantly, he says.

But, he adds, "it is theoretically possible to get liquid water within soil, or under other very special conditions". The question is just how special those conditions need to be, and whether they ever really are found on Mars today.

If there were absolutely no wind, says Christensen, you might build up a stagnant layer of vapour above a liquid surface, preventing it from evaporating too fast. “The problem is, there are winds on Mars… In the real world, I think it's virtually impossible," he told New Scientist.
Simple test

Levin disagrees. He says his analysis shows that there can be wind-free environments at certain times of day in certain protected locations. He thinks that could apply to these small depressions inside the sheltered bowl of Endurance crater, at midday in the Martian summer.

He adds that highly briny water, as is probably found on Mars, could be stable even at much lower temperatures.

Although the rover is now miles away from this site, Levin proposes a simple test that would prove the presence of liquid if similar features are found: use the rover's drill on the surface of the flat area. If it is ice, or any solid material, the drill will leave unmistakable markings, but if it is liquid there should be no trace of the drill's activity.

Levin’s father Gilbert was principal investigator of an experiment on the Viking Mars lander, which found evidence for life on the planet, although negative results from a separate test for organic materials led most scientists to doubt the evidence for biology.

Journal reference: R. L. Levin and Daniel Lyddy, Investigation of possible liquid water ponds on the Martian surface (2007 IEEE Aerospace Applications Conference Proceedings, paper #1376, to be published in IEEE Xplore)

Smooth surface

The smoothness and transparency of the features could suggest either water or very clear ice, Levin says.

"The surface is incredibly smooth, and the edges are in a plane and all at the same altitude," he says. "If they were ice or some other material, they'd show wear and tear over the surface, there would be rubble or sand or something."

His report was presented at a conference of the Institute of Electrical and Electronics Engineers, and will be published later this year in the institute's proceedings.

No signs of liquid water have been observed directly from cameras on the surface before. Reports last year pointed to the existence of gullies on crater walls where water appears to have flowed in the last few years, as shown in images taken from orbit, but those are short-lived flows, which are thought to have frozen over almost immediately.