NASA?s next red planet probe, the Mars Science Laboratory ? now dubbed Curiosity ? has been years in development and overcome numerous hurdles. Now engineers are taking a close look at the car-sized rover?s nuclear power plant.

Engineers preparing the Curiosity rover for its planned launch in 2011 found a slightly faster than expected degradation rate in the rover?s multi-mission radioisotope thermoelectric generator, or MMRTG for short.

The MMRTG is designed to enhance the rover?s range and operability and lifetime on the red planet. The unit uses some 10 pounds (4.8 kg) of plutonium dioxide, mostly plutonium-238, as a heat source.

?Right now we are working with Department of Energy to try and understand it,? McCuistion told, ?but to-date the only impact is expected to be some operational work-arounds in Martian winter?slower operational pace essentially because it?ll take longer to charge the batteries.?

Curiosity?s MMRTG power plant is currently fully fueled and stored at the Idaho National Laboratory, where it is awaiting delivery to the rover?s launch site in Cape Canaveral, Fla., next year [Graphic: How Mars Science Laboratory works].

Optimistic for Mars

The radioisotope thermoelectric generator oddity is the latest in a host of technological teething problems of the now roughly $2.3 billion mission led to a slip in its launch from 2009 to next year.

Although challenges still remain in getting the nuclear-powered rover spiffed up and ready for sendoff to Mars, many of those problems have been resolved ? including a potentially serious issue with the probe?s metal skeleton.

A contractor had falsified documentation as to the quality of titanium it had supplied to the aerospace community. That forced NASA to backtrack through paperwork to assure that the Curiosity rover didn?t use batches of the ?wrong stuff.?

The paperwork to sort through the use of titanium on Curiosity is now over 90 percent complete, ?and no show stoppers, so I am feeling cautiously optimistic that MSL will not be impacted,? said Doug McCuistion, Director of the NASA Mars Exploration Program in Washington, D.C.

Where to land

Meanwhile, the science community is revving up to make use of Curiosity and its suite of science gear.

?The key technological and schedule problems are being solved and the Mars community is quite pleased,? noted John Mustard of Brown University in Providence, Rhode Island. He?s also chair of the Mars Exploration Program Analysis Group, charted by NASA to assist in planning the scientific exploration of the red planet.

This September Mars scientists will take part in the fourth landing site workshop for Curiosity. That meeting will focus on the outstanding science questions and relative merits of the final Mars Science Laboratory?s potential landing sites that remain under deliberation.

According to John Grant of the Smithsonian?s Center for Earth and Planetary Studies and Matt Golombek of the Jet Propulsion Laboratory -- the co-chairs of the Mars Landing Site Steering Committee -- the process of selecting Curiosity?s landing site is converging.

Nearly 60 sites for the mission?s planned touchdown have been mulled over for more than three years. Only Eberswalde crater, Gale crater, Holden crater, and Mawrth Vallis remain.

Grant and Golombek report that each of these sites represents exciting science opportunities for MSL and has been highly rated by the science community. A fifth site may be added to the list, a decision that will be forthcoming in May by the MSL project with input from the MSL Landing Site Steering Committee.

Avatar in red?

Along with an impressive array of research duties, the Curiosity rover?s imaging and scientific suite will be the most capable education and public outreach package ever placed on the surface of another planet ? and given a successful Mars landing promises to provide awesome images and movies.

One new capacity being re-evaluated is to imbue Curiosity with a zoom 3D camera capability. Malin Space Science Systems in San Diego, California is building it for Oscar-winning director, James Cameron, who recently delivered Avatar, his blockbuster cinematic experience.

Cameron is a member of the MSL science team, firmly focused on video documentation and traverse science using the rover?s MastCam, the Mars Hand Lens Imager (MAHLI), and the Mars Descent Imager (MARDI) that will record in ?ride-along video? fashion the final two minutes of landing.

Earlier plans to have MastCam zoom were scrapped to meet acceptable technical, schedule and cost risk standards in 2007. But the idea is back on the table, maybe.

Today, the rover?s fixed MastCam is already built and delivered, and can fly on MSL as planned if the zoom version doesn?t come together in time.

?But if it does, and if it passes qualification tests without holding up the MSL schedule, it could be swapped onto the rover,? NASA spokesman ?Dwayne Brown told ?NASA has tentatively agreed, and is paying for the new work on the zoom, which is expected to cost about $5 million. However, nothing has been confirmed at this time.?

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Leonard David has been reporting on the space industry for more than five decades. He is past editor-in-chief of the National Space Society's Ad Astra and Space World magazines and has written for since 1999.