WHAT'S UP: Curiosity on its way to Mars

Dec 2, 2011

Expected to take more than eight months to make the trip to Mars, NASA’s Mars Science Laboratory (MSL) and robotic rover Curiosity is the most ambitious Mars exploration mission every attempted.

About 10 feet long and weighting in (on Earth) at about 2,000 pounds, Curiosity is about the size of a small automobile.

Curiosity is 10 times heavier and five times larger than NASA’s earlier Mars Exploration Rovers (MERs) Spirit and Opportunity, which have transformed our understanding of the geochemical processing that has occurred Mars’ surface. But the MERs found no signs of life.

NASA’s MERs and MSL systems are mostly targeted on finding signs of life on the Martian surface.

In its search for life, Curiosity is designed to be able to cruise at an average speed of about 100 feet per hour, navigating automatically, and will be able to climb over obstructions — like rocks and Martians that get in its way — nearly 3 feet tall.

The large rover is powered by plutonium marshmallows.

Spacecraft and rovers are often designed to be powered by solar energy. There are no cloudy days in space; but solar panels are large and fragile, and don’t generate all that much energy.

In addition, NASA engineers learned from the MERs that dust on the Martian surface is a problem. The power generated to operate both MERs steadily decreased as Martian dust coated their solar panels.

Curiosity is large and power hungry, compared to the MERs, so NASA engineers went nuclear for this mission. Curiosity is powered by a radioisotope thermoelectric generator, or RTG. RTGs generate electricity directly from heat given off by the decay of a radioactive isotope of heavy elements like uranium and plutonium. They are relatively compact and can produce energy for tens of years, normally.

Curiosity’s RTG contains about 10 pounds of a non-fissile isotope of plutonium, in the form of marshmallow-size pellets. The unit produces about 2,000 watts of heat and about 125 watts of electrical energy.

The electrical energy is used to run Curiosity’s roving motors, cameras, computers and communication equipment, its robotic arm and the on-board science experiments. It’s amazing that all this can be accomplished with an amount of power about equal to that used by a household lightbulb.

Nothing is wasted.

For comparison, my MacBook PC requires an 85-watt power supply.

The heat given off by Curiosity’s RTG is not wasted either. Curiosity will be subjected to extreme day/night temperature variations.

Under the Martian summer sun during the day, temperatures (in Fahrenheit) will rise into the high 80s, but at night will fall to nearly 200 below zero.

Curiosity has an onboard heat management system that uses heat generated by the RTGs to keep the rover warm during the long, cold nights.

When on Mars, Curiosity will rove inside a large crater called Gale Crater, poking and prodding the soil and rocks, searching for signs of life.

Curiosity is expected to work at its mission for nearly two Earth years, before succumbing to the harshness of the Martian environment.

You can read more about the Mars Science Laboratory and follow its progress online at http://mars.jpl.nasa.gov/msl/.

And if you get up and out before the sun rises, you can see Curiosity’s target if you stand facing south and look high overhead. Look for a brightish, reddish star near the constellation Leo — that’s Mars.

— By Doug Furton, a member of the physics faculty at GVSU. Send questions and suggestions to dgf@inbox.com.

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