For months, the spacecraft sat very still in the vast, empty expanse of a shallow Mar plain, alone and undisturbed, except for the thin whine of a strange wind.
Back on Earth, the operators of the Jet Propulsion Laboratory were worried. The purpose of the InSight mission was to track the earthquakes, tremors and tremors of the Red Planet for clues to its interior. But the spacecraft had not even felt a twitch in the ground under his three feet.
"The longer we walked without quakes, the more questionable or dubious we became that we could make science. We came to Mars to do this," said Bruce Banerdt, the mission's lead investigator.
On April 6, the InSight seismometer sensed a faint, eerie rumble ̵
"Eventually," said Banerdt, "we know that Mars is seismically active, we know it talks to us."
Well, he continued, "It's just a matter of being patient, waiting and listening and collecting the quakes as they come along."
Scientists have long been trying to explain how Mars, which is very similar to Mars Earth looked as the two bodies formed 4.6 billion years ago, the bleak desert world was seen today. Most believe that the inner dynamo of the Red Planet could be the culprit. Constant bulging of the earth creates a magnetic field that protects our surface from radiation and helps us keep our atmosphere. Evidence from ancient rocks, however, indicates that the magnetic field of Mars has stalled about 3 billion years ago.
InSight wants to find out what happened to seismic waves – the subterranean waves created by earthquakes – as probes.
"It's almost like an X-ray," said Banerdt. The spacecraft's exquisitely sensitive seismometer can track subtle changes in the waves as they travel through the Martian crust, mantle, and core.
"Every time you have a Martian Earthquake that gives you another slice through the planet," Banerdt said. "At some point, we want to build some of those discs to create a 3-D image of what's in it."
But it takes a quake to create these waves – and none seemed to happen.
Banerdt slept In his California home, a new batch of InSight data was sent from the Martian surface to seismologists in Switzerland. The scientists noticed a consistent and sustained signal in the data. It was unlike the sporadic shaking they were used to seeing from gusts of wind and the crackle and crackle of the spaceship, which warmed and cooled under the sun.
When Banerdt woke up, an urgent text message appeared on his screen: "Conference call in half an hour."
"I jumped out of bed right away," he recalls. "It was exciting."
Scientists traded PowerPoint slides and discussed interpretations. In a recording published by NASA that accelerates the seismic wave frequencies to make them audible to human ears, the signal sounds almost like a plane flying.
Finally, they decided that the signal must be very strong small quake – about strength 2 or 2.5. Dozens of tremors, as they occur daily in Southern California, completely unnoticed in the noise of human activity and ocean waves.
The signal of Mars was also extended; It took almost 10 minutes, unusual for such a small seismic event. This is probably a result of fractures in the Martian crust that bounce signals like echoes in a labyrinthine cave.
The signal Banerdt described on Tuesday in a Keynote address by the Seismological Society of America warn It was not big enough to act as the kind of "X-ray" scientists hoped to find. But it is still "like a catnip" for her, said Banerdt.
"This is a whole new planet that we open up to seismology," he said.
Models using the new discovery suggest that the spacecraft should witness up to a few dozen quakes during its two-year mission.
"It's getting a bit sparse and tight. We really need to compress the data as much as possible, "said Banerdt. "But we are in the right arena to do this kind of science."