InSight mission to find what lies beneath Martian surface
BY STEPHEN CLARK
Posted: March 30, 2013
HOUSTON -- NASA's next Mars lander will launch in 2016 to take the red planet's pulse and temperature, listening for tremors, measuring underground heat and monitoring the wobble in its rotation to answer fundamental questions about what lies beneath the desert world's rust-colored surface.
"The InSight mission is a geophysical mission to Mars," Banerdt said. "It's going to go to Mars and take its vital signs. It's going to take its heartbeat - the seismic activity of the planet. It's going to take its temperature by measuring the thermal gradient of its surface, which tells us how much heat is coming out. And it's going to measure its reflexes by looking at how its rotation wobbles with the tidal effects of the sun."
Based on a proven lander design successfully demonstrated by NASA's Phoenix mission in 2008, the InSight spacecraft will make a rocket-assisted touchdown in a region named Elysium Planitia, a broad equatorial plain dotted with extinct volcanoes.
"It's very flat," Banerdt said. "There are lava flows nearby, and we have already picked out landing ellipses around the flow."
Banerdt is a researcher based at NASA's Jet Propulsion Laboratory in Pasadena, Calif.
Teams identified 16 potential landing zones around the western side of Elysium Planitia. All of the ellipse-shaped landing site candidates meet the lander's engineering constraints, which stipulate an area of sufficiently low altitude to allow the spacecraft to safely make a parachute- and rocket-assisted descent.
InSight also needs a flat landing area free of large rocks with penetrable soil to a depth of at least 5 meters, or about 15 feet. The mission's two main instruments, a seismometer and drilling heat probe, require a site with soft rock-free soil.
According to a presentation by Matt Golombek, a geologist at JPL, the list of 16 candidate landing sites will be whittled down to and a half-dozen locations by the end of this year. Officials will select two or three finalists by the end of 2014, ultimately leading to a final decision on InSight's destination by the end of 2015.
A high-resolution camera on NASA's Mars Reconnaissance Orbiter will take detailed photos of each landing ellipse throughout the process, looking for hazards such as steep slopes and boulder fields.
Unlike NASA's Curiosity rover, which targeted a science-rich landing site on the flank of a three-mile-high mountain, InSight's landing site will be selected based solely on engineering and safety considerations.
The three-legged InSight lander, built by Lockheed Martin Corp., will set down on Mars in September 2016, starting a surface mission expected to last at least two years.
InSight was selected by NASA in August as the next project in the agency's Discovery program, which fields planetary exploration missions on tightly-controlled budgets. InSight's cost to NASA is capped at $425 million, excluding launch vehicle costs.
Engineers know the capabilities and limits of the Phoenix lander system, which was originally designed for a mission that was supposed to launch in 2001. The 2001 lander, named Surveyor, was canceled in the wake of the back-to-back failures of NASA's Mars Climate Orbiter and Mars Polar Lander missions in 1998.
The understanding will keep InSight's costs under control and simplify the mission's development, Banerdt said.
The stationary lander design, with its roots in the late 1990s, showed exemplary performance during the Phoenix mission, which launched in 2007 and touched down on the red planet's northern polar plains in May 2008.
The biggest change from the Phoenix spacecraft to InSight is a suite of new instruments. Instead of analyzing soil and scouring the surface for signs of ice, as Phoenix did, the InSight mission will deploy a seismometer to make the first direct measurements of Mars quakes. The lander will also employ a hammering drill to burrow up to 15 feet underground, taking temperature readings to measure heat changes at different layers immediately beneath the Martian surface.
The French space agency, CNES, is providing InSight's $42 million seismometer. Germany is funding the lander's underground heat probe.
Scientists will also analyze radio signals bouncing between Earth and the InSight spacecraft, detecting tiny wobbles in the red planet's rotation, revealing properties of the Martian core.
"Mars is kind of the Goldilocks planet," Banerdt said. "It's not too big, it's not too small, it's just right. If it was too big, it would have retained a lot of activity and erased all the evidence that we're looking for. If it was too small, it never would have undergone the same processes that formed the Earth."
Among others, InSight will address questions such as:
Up to now, Banerdt said, scientists could only guess answers to such questions.
"We are missing cold, hard data, and this is what this mission will provide," said Suzanne Smrekar, InSight's deputy principal investigator based at JPL.
"We've done a lot of exploring on the surface of Mars, and we have missions coming up to study the atmosphere," Banerdt said, referring to a pair of upcoming spacecraft - NASA's MAVEN mission and Europe's Trace Gas Orbiter - focused on the Martian atmosphere.
MAVEN will launch in November, and the Trace Gas Orbiter is scheduled to launch in January 2016, two months before InSight.
"But when it comes to what's below the surface of Mars, we don't understand as much," Banerdt said. "We are plugging that last big hole in the basic understanding of Mars."
Don't expect InSight to produce color panoramic images like the Curiosity rover. The lander will carry a set of black-and-white cameras, utilizing spares left over from NASA's rover missions to save money, according to Banerdt.
The cameras will monitor movements of the lander's robotic arm as it picks up the seismometer and drill instruments from the spacecraft's payload deck and places the devices on the Martian surface.
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