Thursday, December 2

Leaks in Instrument Force NASA to Delay Mars Mission Until 2018



NASA’s next Mars mission will remain earthbound for at least two years.

Officials at the space agency announced on Tuesday that its Mars InSight mission will miss its March 2016 launch date, because of stubborn tiny leaks in a vacuum sphere housing its seismic instrument.

“We just have run out of time,” John M. Grunsfeld, the associate administrator for NASA’s science directorate, said during a telephone news conference.

During a test on Monday at ultracold temperatures, about minus 50 degrees Fahrenheit, a leak was again observed.

NASA’s Mars missions so far have largely explored the surface geology and properties of Mars. The instruments aboard InSight — a shortening of Interior Exploration using Seismic Investigations, Geodesy and Heat Transport — are designed to listen to what is going on in the deep interior of the planet.

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Because Mars, farther from the sun, takes longer to orbit, Earth and Mars will not be in alignment again for 26 months, in May 2018. Dr. Grunsfeld said it would take about two months to review the ramifications of the delay and the options of what to do next.

About $525 million of the mission’s $675 million budget has been spent.

CNES, the French space agency, is in charge of InSight’s seismic instrument, which is to be placed on the surface to measure the vibrations of marsquakes and the impacts of meteorites. As with sonograms, the change of velocity of sound waves passing through the planet would enable scientists to infer the depths of Mars’ crust, mantle and core.

The three seismometers in the instrument, sensitive enough to detect vibrations as slight as the width of an atom, require a near-perfect vacuum for precise measurements.

The seismometers sit within a sphere about nine inches in diameter. Bruce Banerdt, InSight’s principal investigator, said that during tests of the instrument, still in France, air was pumped out to a pressure of about one ten-millionth of a millibar, or less than a billionth of the Earth’s atmospheric pressure of about 1,000 millibars.

Over the course of the mission, the vacuum would gradually rise by a factor of 10,000, to about a thousandth of a millibar, because of gases released within the instrument. Dr. Banerdt said the instrument would still function if the pressure were 100 times higher, at a tenth of a millibar.

But the leaks were large enough that the pressure inside rose to two tenths of a millibar over the course of a few days, “which is by most standards a pretty darn good vacuum,” Dr. Banerdt said. “But for our purposes, we needed a better vacuum than that.”

Engineers first discovered the leaks in August. Each time they thought they had sealed the last leak, another one appeared.

Dr. Grunsfeld said that if the seismometers did not work, “in some sense, we don’t have a decision to make, because we’re not ready to go.”

Lockheed Martin, the manufacturer of the spacecraft, had already shipped InSight to Vandenberg Air Force Base in California, where it was to be launched on an Atlas 5 rocket. The spacecraft will now probably be sent back to Lockheed Martin in Denver and put into storage.

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