Block Island—a half-ton meteorite found on Mars by NASA's Opportunity rover.Image credit, NASA/MER OpportunityEver been driving down a lonely desert highway when you suddenly glimpse something in the corner of your eye that makes you think, "What was that?!" You brake, tires screech, you spin the wheel and make a wild U-turn, cutting into the shoulder and leaving a rooster-tail of dust as you floor the gas to get back to what you thought you saw….

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.

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.

Picture of the edge of Victoria Crater superimposed with
image of the rover Opportunity.
Credit: NASA/JPLMars is not only on the horizon, it's become a sky-high creature of the night…and so, it's time to blog about the Red Planet once again, and to showcase a few favorite pictures from the veteran robots presently exploring that world.

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