Tag Archives: moonquake

Stunning animation shows how Marsquakes look like

The Earth has lots of earthquakes, but it’s not the only place with temblors. While Martian quakes are much smaller in intensity, they do exist — here’s how the seismic waves propagate through the planet:

Seismic waves from a marsquake as they move through different layers of the Martian interior. Credits: NASA/JPL-Caltech/ETH Zurich/Van Driel

Seeing the inside

When NASA sent astronauts to the moon in the Apollo 11 mission, they also had them deploy scientific instruments — including seismometers. But it took a couple more decades until the agency’s InSight lander brought the first seismometer to Mars in late 2018. Called the Seismic Experiment for Interior Structure (SEIS), the seismometer made history in April 2019, when it detected the first marsquake.

The mission is led by researchers at ETH Zurich in Switzerland who monitor and analyze the data. Because Mars doesn’t have active plate tectonics, it also has much fewer (and less intense) earthquakes. These temblors pose no realistic risk whatsoever — the purpose of the seismometer is to help researchers better understand the inside of the planet.

InSight’s seismometer has a cozy shelter on Mars. Credits: NASA.

Much of what we know about Earth’s internal structure also comes from seismology. When an earthquake occurs, it spreads out energy in the form of seismic waves. There are different types of waves which propagate differently through the Earth’s inside. By calculating the time of arrival between different types of waves, their amplitude, and several other parameters, seismologists make certain deductions about the Earth’s structure.

In a way, it’s a bit like how an ultrasound reading can reveal a baby inside a mother’s womb, except the scale and accuracy of the procedures is very different. Ultrasounds and seismic waves are both acoustic waves and they get similarly reflected and refracted. But researchers didn’t stop here.

Feeling a marsquake

Researchers at ETH took things even further: they wanted to see how a marsquake feels, compared to one on Earth or on the moon.

Of course, since the marsquake is much weaker than its earthly equivalent, the signal is also weaker. The team had to amplify the marsquake signals by a factor of 10 million in order to make the barely-perceptible tremors comparable to earthquakes. Moonquakes were similarly amplified.

The reason why quakes on different types of planets can feel differently is that they are affected by the material the waves pass through. We’re still in the very early days of studying marsquakes but so far at least, the results are encouraging.

The 2020 Mars Rover will also feature an instrument that will help researchers “see” beneath the Martian surface. The ground penetrating radar will use electromagnetic waves to create a high-resolution visualization of a Martian subsurface, at depths of up to 10 meters.

Earth’s gravity pull is opening cracks and faults on the Moon

Just as the Moon is causing waters on Earth to go up and down (tides), so too does the Earth affect the Moon. Recently, researchers have found that our planet’s gravitational pull is having a deep effect on our satellite, opening new cracks and faults on its surface.

Lunar Reconnaissance Orbiter Camera images have revealed thousands of young, lobate thrust fault scarps on the moon. Image released Sept. 15, 2015.
Credit: NASA/LRO/Arizona State University/Smithsonian Institution

“We know the close relationship between the Earth and the moon goes back to their origins, but what a surprise [it was] to find the Earth is still helping to shape the moon,” study lead author Thomas Watters, a planetary scientist at the Smithsonian Institution’s National Air and Space Museum in Washington, D.C., told Space.

They analyzed data from NASA’s Lunar Reconnaissance Orbiter (LRO), which launched in 2009 – there’s an abundance of data from the LRO that is yet to be properly analyzed. They discovered 14 lobe-shaped fault scarps, or cliffs. These are among the most common geological features on the planet, likely forming as the hot interior cooled and contracted, causing the solid crust to crack.

However, if the only factor creating these cracks was the Moon’s interior cooling down, then you’d expect their orientation to be random; however, they are anything but random.

“It was a big surprise to find that the fault scarps don’t have random orientations,” Watters said. Instead, “there is a pattern in the orientations of the thousands of faults, and it suggests something else is influencing their formation, something that’s also acting on a global scale,” Watters said in a statement. “That something is the Earth’s gravitational pull.”

Basically, they found that most scarps are oriented where the Earth’s pull is the strongest. Many are lined up north to south at low and mid latitudes near the moon’s equator and east to west at high latitudes near the moon’s poles – either in the closest areas to the Earth, or the farthest ones away. When they created a model to take Earth’s gravity into account, it closely match the observed data.

“With LRO, we’ve been able to study the moon globally in detail not yet possible with any other body in the solar system beyond Earth, and the LRO data set enables us to tease out subtle but important processes that would otherwise remain hidden,” John Keller, LRO project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said in a different statement.

It’s quite possible that these cracks are active right now, opening from time to time due to the Earth’s attraction. If this is the case, then there are likely “moonquakes”, which a network of seismometers could one day pick up.