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Asteroids Rock

By David Reneke

David Reneke brings news from the space and astronomy communities around the world.

After a decade of planning by science teams, NASA’s Dawn spacecraft has returned the first close-up image after beginning its orbit around the giant asteroid Vesta. On 15 July Dawn became the first probe to enter orbit around an object in the main asteroid belt between Mars and Jupiter.

“We just sort of slid into orbit, letting gravity grab the spacecraft with a light tug,” one NASA technician was overheard saying. Neat huh?

The first images snapped from as little as 16,000 km away have been startling, showing Vesta in greater detail than ever before. This enigmatic little world is a remnant of the formation of the solar system, the flotsam and jetsam left over from the creation of the planets around five billion years ago. Dawn was launched in September 2007.

Vesta is 530 km in diameter and the second most massive object in the asteroid belt behind Pallas and Juno. Early ground-and later space-based telescopes have scoured the surface of Vesta but, until now, haven’t been able to see much detail on its surface.

Most space scientists agree that this region of space we call the asteroid belt has been ignored for far too long. The rubble pile here represents pristine pieces of a nascent solar system. Vesta is thought to be the source of a large number of meteorites that fall to Earth.

“We’re beginning the study of arguably the oldest extant primordial surface in the solar system,” said Dawn principal investigator Christopher Russell of the University of California, Los Angeles.

After travelling for nearly 4 years and 2.8 billion km, Dawn also accomplished the largest propulsive acceleration of any spacecraft, with a change in velocity of more than 6.7 km/s, due to its ion engines. The engines expel ions to create thrust and provide higher spacecraft speeds than any other technology currently available.

Dawn will spend a year orbiting Vesta and then travel to the dwarf planet Ceres, arriving in February 2015.

The Dawn team will soon begin gathering data. Observations will help scientists understand the earliest chapter of our solar system. The data will also help pave the way for future human space missions.

Mars Under the Microscope
We’ve got Moon rocks from the lunar surface, gossamer-sized wisps of cometary material from the Hyabusa mission and a few sprinklings of what we believe are Martian meteorites. But exobiologists have yet to hold a genuine red rock from the Red Planet.

Many planetary scientists believe this is the only way we’ll ever be able to truly figure out if the biomarkers of life exist in the soil or rock strata. You can’t beat examining the real thing under laboratory conditions here on Earth.

A sample return mission is certainly a possibility, but that’s in the future. For now, we want to get a sophisticated lab there and really rake the surface.

Scheduled to launch no later than18 December 2011, the Mars Science Laboratory is part of NASA’s Mars Exploration Program, a long-term effort of robotic exploration of our mysterious neighbour. This rover is going to be much bigger than anything landed there before.

Serving as an entrée to the next decade of Mars exploration, it’s a mobile laboratory that will assess whether Mars ever was, or is still today, able to support microbial life. In other words, its mission is to determine, finally, the planet’s habitability.

The Mars Science Laboratory will rely on new technological innovations, especially for landing. The spacecraft will descend on a parachute and then, during the final seconds prior to landing, lower the upright rover on a tether to the surface, much like a sky crane.

Once on the surface, the rover will be able to roll over obstacles up to 75 cm high and travel up to 90 m/h – blazingly fast for a Mars rover! A radioisotope power system that generates electricity from the heat of plutonium’s radioactive decay will ensure operational longevity.

This mission will represent a huge step in Mars surface science and exploration capability because not only will it pave the way for a sample return flight, it’ll also allow for the collection and study of a more diverse range of rock and soil samples from regions not previously visited.

David Reneke is an astronomy lecturer and teacher, a feature writer for major Australian newspapers and magazines, and a science correspondent for ABC and commercial radio. Subscribe to David’s free Astro-Space newsletter at www.davidreneke.com