For the first time ever, humans have detected a likely seismic event on Mars — or a "Marsquake."
The faint seismic signal was measured and recorded by NASA's InSight lander on April 6, the lander's 128th Martian day, or sol. It's the first recorded trembling that apparently originated inside the planet, NASA explains in a statement, as opposed to being caused by forces above the surface, like wind. Scientists are still studying the data to figure out the exact cause of the signal.
If this does turn out to be a Marsquake, it would be the first seismic event detected on the surface of any world other than the Earth and its moon, the BBC reports. NASA released this audio clip of the event:
This seismic event was too small to shed much light on the interior of Mars, which is one of InSight's main objectives, but it's still a big step for the mission. The Martian surface is much quieter than Earth's, NASA explains, letting InSight's specially designed seismometer pick up faint rumbles that would be lost in the noise of Earth's surface.
"We've been waiting months for a signal like this," says Philippe Lognonné, a member of the InSight team at the Institut de Physique du Globe de Paris, in a statement from NASA. "It's so exciting to finally have proof that Mars is still seismically active. We're looking forward to sharing detailed results once we've had a chance to analyze them."
The Mars lander InSight survived its "7 minutes of terror" and successfully touched down on the red planet on Nov. 26. After that drama, the lander got itself up and running, snapping the picture at the top of this page with its Instrument Deployment Camera.
The image was shared on NASA's social media channels with a caption from InSight's perspective. "There's a quiet beauty here," someone wrote for the lander. "Looking forward to exploring my new home."
This wasn't the first image taken by InSight, however; it was just the prettier of the two. Using the Instrument Context Camera, the lander also took a grainy photo of the surface (above), explaining that it hadn't taken the lens cover off but was simply too excited to wait. "My first picture on Mars! My lens cover isn’t off yet," the Facebook caption read, "but I just had to show you a first look at my new home."
'The InSight lander acts like a giant ear'
Following these images, InSight captured its first audio recording on Dec. 1. Two sensors on the lander recorded a low rumble, similar to thunder, that was caused by vibrations in wind blowing 10 to 15 mph. The air-pressure sensor recorded the air vibrations directly, and the seismometer recorded the lander's vibrations when the wind moved across its solar panels.
"The InSight lander acts like a giant ear," said Tom Pike, InSight science team member and sensor designer at Imperial College London. "The solar panels on the lander's sides respond to pressure fluctuations of the wind. It's like InSight is cupping its ears and hearing the Mars wind beating on it. When we looked at the direction of the lander vibrations coming from the solar panels, it matches the expected wind direction at our landing site."
The seismometer will analyze vibrations from Mars' deep interior and will hopefully determine if tremors on the red planet are similar to earthquakes.
"Capturing this audio was an unplanned treat," said Bruce Banerdt, InSight principal investigator at NASA's Jet Propulsion Laboratory. "But one of the things our mission is dedicated to is measuring motion on Mars, and naturally that includes motion caused by sound waves."
'An awesome Christmas present'
InSight deployed its seismometer on Dec. 19, the first time in history that such an instrument has been placed on the surface of another planet. After verifying that Insight's robotic arm was functioning, NASA engineers commanded the lander to place its seismometer on the ground as far away as the arm can reach — 5.367 feet, or 1.636 meters.
"Seismometer deployment is as important as landing InSight on Mars," Banerdt said in a statement. "The seismometer is the highest-priority instrument on InSight: We need it in order to complete about three-quarters of our science objectives."
After leveling the seismometer from its slightly tilted initial position, engineers still needed some time to analyze the incoming seismic data. But InSight project manager Tom Hoffman was just thankful to have made it so far so quickly.
"InSight's timetable of activities on Mars has gone better than we hoped," Hoffman said. "Getting the seismometer safely on the ground is an awesome Christmas present."
InSight shows off for the camera
A few days after reaching Mars, InSight also took its first selfie. The image shows the lander's dock and solar panels plus its weather sensor booms, science instruments and UHF antenna on top of the lander.
InSight — which stands for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport — will stay put, unlike the rovers. In addition to its seismometer, it also placed a heat probe on Mars, all in an effort to gain a better understanding of the planet's interior, including its core. This, it's hoped, will offer some details about how the planets of the inner solar system — Mercury, Venus, Earth and Mars — formed.
InSight's mission is expected to last at least two years.
Editor's note: This article has been updated since it was originally published in November 2018.
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