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Image: NASA/JPL-Caltech

Terrifying landing

John Blau / Holly Cooper
July 30, 2012

NASA's Mars rover is on its final approach for the Red Planet. But whether it lands - or crashes and burns - depends on what will be a blind, seven minutes of terror on Earth.


The American space agency's Mars Science Laboratory - commonly called Curiosity - will face a critical seven minutes as it enters the atmosphere of Mars.

It will have just these seven minutes to decelerate from 13,000 miles per hour (21,000 kph) to zero.

This critical stage is known as the seven minutes of terror.

The seven minute landing is expected late in the evening of August 5 (Pacific Daylight Time or early in the morning on August 6 European Daylight Time).

But it will take twice that long (14 minutes) for signals from Curiosity to reach Earth. So by the time NASA gets word of the rover entering the Martian atmosphere, Curiosity will already have been on the surface for seven minutes - dead or alive.

Curiosity Landing Site in Gale Crater This oblique, southward-looking view of Gale crater shows the mound of layered rocks that NASA's Mars Science Laboratory will investigate. The mission's selected landing site is just north of the mound inside the crater. Gale crater is 96 miles (154 kilometers) in diameter and holds a layered mountain rising about 3 miles (5 kilometers) above the crater floor. The landing site contains material washed down from the wall of the crater, which will provide scientists with the opportunity to investigate the rocks that form the bedrock in this area. The landing ellipse also contains a rock type that is very dense and very bright colored; it is unlike any rock type previously investigated on Mars. It may be an ancient playa lake deposit, and it will likely be the mission's first target in checking for the presence of organic molecules. The area of top scientific interest for Mars Science Laboratory is at the base of the mound, just at the edge of the landing ellipse. Here, orbiting instruments have detected signatures of both clay minerals and sulfate salts. Scientists studying Mars have several important hypotheses about how these minerals reflect changes in the Martian environment, particularly changes in the amount of water on the surface of Mars. The Mars Science Laboratory rover, Curiosity, will use its full instrument suite to study these minerals and how they formed to give us insights into those ancient Martian environments. These rocks are also a prime target in checking for organic molecules. This three-dimensional perspective view was created using visible-light imaging by the Thermal Emission Imaging System camera on NASA's Mars Odyssey orbiter. Three-dimensional information was derived from observations by the Mars Orbiter Laser Altimeter, which flew on NASA's Mars Global Surveyor orbiter. Color information is derived from color imaging of portions of the scene by the High Resolution Imaging Science Experiment camera on NASA's Mars Reconnaissance Orbiter. The vertical dimension is not exaggerated. The Mars Science Laboratory spacecraft is being prepared for launch during the period Nov. 25 to Dec. 18, 2011. In a prime mission lasting one Martian year -- nearly two Earth years -- after landing, researchers will use the rover's tools to study whether the landing region has had environmental conditions favorable for supporting microbial life and for preserving clues about whether life existed. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Science Laboratory Project for NASA's Science Mission Directorate in Washington. Arizona State University, Tempe, operates the Thermal Emission Imaging System. The Mars Orbiter Laser Altimeter was operated by NASA Goddard Space Flight Center, Greenbelt, Md. The University of Arizona, Tucson, operates the High Resolution Science Imaging Experiment. JPL manages Mars Odyssey and Mars Reconnaissance Orbiter for NASA's Science Mission Directorate. Image Credit: NASA/JPL-Caltech/ASU/UA
Curiosity is heading for Gale Crater near the equator of MarsImage: NASA/JPL-Caltech/ASU/UA

Blind exploration

It has also been described as a blind landing because the satellite that NASA was counting on for real-time coverage of the Mars Science Laboratory's descent was sidelined by a maneuvering system glitch.

Doug McCuistion, NASA's Mars exploration program chief, said at the time that there would be "no impact to landing itself. It's simply how that data gets returned to us and how timely that data is."

At NASA's request, the European Space Agency's (ESA) Mars Express will now be in position to observe the landing.

The Mars Express has remained in orbit of the planet since December 2003 when its Beagle 2 lander failed.

Mars Express spacecraft operations manager, Michel Denis, says the ESA will provide crucial back-up to NASA's own tracking systems if anything goes wrong.

"It will be a great day for space science," says Denis, who believes Curiosity's landing will be a success - although he admits there are no guarantees in space.

Ready to roll

During landing the rover will have to complete a sequence of highly complicated logistical maneuvers, controlled by its onboard computer.

First the atmosphere of Mars will help reduce Curiosity's speed by about 12,000 mph. Mars' atmosphere is 100 times thinner than Earth's and this will have a drag effect.

The landing parachute was tested in 2009 inside the world's largest wind tunnel
The landing parachute was tested in 2009 inside the world's largest wind tunnelImage: NASA/JPL-Caltech

Then the craft will release a parachute. The 100 pound (45 kg) parachute will have to withstand 65,000 pounds of force. Once the craft's heat shield separates at 370 mph and the parachute is shed, reverse rockets will activate to stabilize it.

Decelerating from 70 mph to 2 mph, the capsule will lower the Mars rover onto a sky crane from 25 feet (7.62 meters) to wheels down on the surface.

It is hoped that all this will happen - without a hitch - while officials at NASA wait the seven grueling minutes for their first sign of success.

But the ESA's Michel Denis says that once Curiosity has successfully landed on the surface of Mars it will be ready to roll.

"It will be like getting a new car right from the dealer," says Denis.

Size matters

And the rover is almost literally the size of a sports utility vehicle - 7 feet tall, 9 feet wide, 10 feet long, and 2,000 pounds. Curiosity is the biggest and best equipped rover ever to head to another planet, taking the search for alien life to a new level.

Curiosity dwarfs its ancestor Sojourner, the 23-pound rover that was the first to move around Mars in 1997. It is bigger than the 400-pound Mars Exploration rovers, Spirit and Opportunity, which landed in 2004.

The new machine is also faster at 3.35 mph, compared with Opportunity's top speed of 0.1 mph.

Curiosity - NASA's Mars rover
The rover could be NASA's last Mars mission for a whileImage: NASA/JPL-Caltech

Speed is not everything - survival is. Opportunity continues to explore a massive crater called Endeavour. It has logged 21.4 miles and still sends valuable data.

Possible last landing

But with a price tag of $2.5 billion (2.1 billion euros), Curiosity is NASA's most expensive mission to Mars. And over budget at $1 billion, it could well be NASA's last landing on the Red Planet for the foreseeable future.

The goal of the two-year mission is to explore Gale Crater - which is near Mars' equator - and search for evidence of any life.

Curiosity is equipped to do just that. The six-wheeled robot can shoot lasers at rocks to measure their chemical compositions and take high-resolution video of the Martian landscape, which pending a successful landing will be relayed to Earth.

The rover is covered with sensors and cameras and has a long robotic arm equipped with a fistful of tools. It has a scooper to collect soil samples, a drill to bore into stone and a high-sensitivity lens to examine microscopic structures measuring only 12.5 microns.

"All Mars exploration helps the overall space community," says Peter Hulsroj, director of the European Space Policy Institute (ESPI). "Exploring Mars is a step-by-step endeavor and Curiosity is a wonderful step."

Since efforts to explore Mars started in 1960, the US, Europe, Russia and Japan have launched 40 missions. But more than half have crashed, malfunctioned or disappeared.

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