A Rover that Can Rove
On Nov. 26, 2011, an Atlas V launched a MiniCooper-sized space craft towards a rendezvous with Mars. The craft is named Curiosity. It is NASA’s newest Mars Rover. It is far different from Spirit, Opportunity and Sojourner, which have preceded it. It is much larger, far more sophisticated, and not dependent on the Sun for power. It will touch down on our neighbor in August of 2012.
Curiosity, officially the Mars Science Laboratory (MSL), is nine feet long, and weighs 7500 pounds, four times as much as the previous rovers. It will travel on six metal wheels, each powered by its own electric motor. The wheels are 20 inches in diameter giving the rover the ability to climb over obstacles 30 inches high. The front and rear wheels will be steerable, controlled by electric motors. This will enable Curiosity to turn 360 degrees in place.
We mentioned Curiosity would not need the Sun for power. Rather than solar panels, it has an atomic battery. This is a ‘battery’ that produces electricity from the radiation of a radioactive substance impinging on a target that generates electricity due to that radiation. This means Curiosity can operate night and day. It will not be affected by sand storms. Its atomic battery should last for years.
The Mars Science Lab package Curiosity carries, holds 10 very sophisticated experiments and pieces of equipment. One of the most unique is a high powered laser Curiosity will fire at interesting rocks to determine their composition. The laser will vaporize a tiny spot on the rock, and a spectroscope will analyze the plasma to determine the chemical makeup of the rock. This can be done from as much as 40 feet away, and at full speed.
Another unique piece of equipment is SAM—that’s Sample Analysis at Mars. This is a ‘sniffer’ that will take atmospheric samples to try to detect traces of methane in the air. Methane can be produced by microbes, or by liquid water reacting with subterranean rocks.
The MSL of course includes a camera for pictures of the landscape. But it also includes a second camera—the MAHLI—Mars Hand Lens Imager. You readers who are photographers might think of this as a digital camera with a super macro lens. It will give geologists the ability to look at rocks, soil and dust particles in the centimeter to micrometer range.
Most of this equipment (except the sniffer) is mounted on Curiosity’s robotic arm. This arm, as on other landers, is used to pick up samples or dig in the soil to search for samples beneath the surface.
Also on the arm is the Alpha Particle X-Ray Spectrometer (APXS). After the laser finds an interesting sample, this package will analyze its complete chemical composition
A New Landing System
Previous landers and rovers have used various landing techniques to touch down gently on the Martian surface. The first landers like Viking used a solid rocket to slow the descent. The current rovers used both rockets and air bags to cushion the landing, bouncing the rovers along the surface.
Curiosity will land with rockets, but in its own unique way, hanging from a descent stage by cables.
The descent will begin like all have, first with entry into the Martian atmosphere protected by a heat shield. Then the heat shield will be jettisoned and a parachute deployed at about six miles to further slow the descent.
About a mile above the Martian surface, the parachute is jettisoned and the eight rocket motors on the descent stage ignited. At this point the rover is still snugly held against the descent stage, called by NASA the ‘rocket backpack.’
About 66 feet above the surface, the cables begin to spool out and four of the rocket engines shut down. Curiosity is now hanging from the ‘backpack’ much in the same way the giant Skycrane helicopter carries a load. When the wheels touch the surface, the cables automatically release, and the backpack veers away to crash into the surface.
Curiosity is on Mars ready to look for signs of life.
The Curiosity rover’s mission is to search for signs of life—existing today or that existed in the past. It will land in the Martian wetlands—areas that have been chosen because they appear from images taken by the Mars Reconaissance Orbiter to show signs of having once been lakes or in wet conditions.
The landing site will be Gales Crater, a huge crater 96 miles in diameter. Its fasination for Mars explorers is one side shows what appears to be an alluvial fan—a sign of ancient water courses. It is here that Curiosity will touch down, and perhaps find sign of ancient Martian life.
MSL launch: NASA https://www.nasa.gov/multimedia/imagegallery/image_feature_2117.html
Curiosity on Mars: NASA https://www.nasa.gov/images/content/482680main_PIA09201-full.jpg
Curiosity’s laser firing:: NASA https://www.nasa.gov/images/content/482680main_PIA09201-full.jpg
Curiosity landing sequence: NASA https://www.nasa.gov/mission_pages/msl/multimedia/gallery/pia13282.html
Rover hanging from rocket backpack: NASA https://science.nasa.gov/media/medialibrary/2009/10/30/30oct_curiosity_resources/landing.jpg
Gales crater: NASA https://www.nasa.gov/mission_pages/msl/multimedia/gallery/pia14290.html