Seismic Waves Reveal Surprising New Information About Mars

Wavefield simulation on Mars. The first observation of surface waves on Mars reveals details of the planet’s crust. Kim et al., (2022) Science. Credit: ETH Zurich / Doyeon Kim, Martin van Driel, and Christian Boehm

Researchers have observed seismic waves traveling throughout the surface of a planet other than Earth for the first time after two large meteorite impacts on Mars.

Researchers at ETH Zurich’s Marsquake Service have been studying data from the NASA InSight mission’s seismometer on one of our neighboring planets. For over three years, the only seismic waves identified on Mars were those that traveled through the planet’s depths from each quake’s focus or hypocenter. However, the scientists had always hoped for an event that would also cause waves to move throughout the planet’s surface. On December 24, 2021, a meteorite impact on Mars produced the kind of surface waves they had been longing for, finally rewarding their wait.

Atypical features in the quake measurements prompted the researchers to assume that the source was near the surface, so they contacted colleagues who were working with a Mars probe orbiting the planet. Images taken by the Mars Reconnaissance Orbiter in late December 2021 revealed a massive impact crater around 3,500 kilometers from InSight.

Seismic Waves Reveal Surprising New Information About Mars

Wavefield simulation labeled. Kim et al., (2022) Science. Credit: ETH Zurich, Doyeon Kim, Martin van Driel, and Christian Boehm

“The location was a good match with our estimates for the source of the quake,” says Doyeon Kim, a geophysicist and senior research scientist at ETH Zurich’s Institute of Geophysics. Kim is the lead author of a study that has recently been published in the journal Science. The researchers were also able to pinpoint a meteorite impact at just under 7,500 kilometers (about 5,000 miles) from InSight as the source of a second atypical quake.

Each earthquake’s hypocenter was at the surface, therefore in addition to generating seismic body waves like those of earlier marsquakes with deeper hypocenters, they also sent out waves that propagated along the surface of the planet.

“This is the first-time seismic surface waves have been observed on a planet other than Earth. Not even the Apollo missions to the Moon managed it,” Kim says.

What makes the seismic surface waves so important to researchers is that they provide information about the structure of the Martian crust. Seismic body waves, which travel through the planet’s interior during a quake, have so far provided insights into Mars’s core and mantle, but have revealed little about the crust away from the lander itself.

A surprising result

“Until now, our knowledge of the Martian crust has been based on only a single point measurement under the InSight lander,” Kim explains. The result of the surface wave analysis surprised him. On average, the Martian crust between the impact sites and InSight’s seismometer has a very uniform structure and high density. Directly below the lander, however, the researchers had previously detected three layers of crust that implied a lower density.

The new findings are remarkable because a planet’s crust provides important clues about how that planet formed and evolved. Since the crust itself is the result of early dynamic processes in the mantle and subsequent magmatic processes, it can tell us about conditions billions of years ago and the timeline of impacts, which were particularly common in Mars’ early days.

Kim explains how the new measurement was made, “The speed at which surface waves propagate depends on their frequency, which in turn depends on their depth.” By measuring changes in velocity in the seismic data across different frequencies, it is possible to infer how the velocity changes at different depths because each frequency is sensitive to different depths. This provides the basis for estimating the average density of the rock because the seismic velocity also depends on the elastic properties of the material through which the waves travel. This data allowed the researchers to determine the structure of the crust at depths between roughly 5 and 30 kilometers below the surface of Mars.

Greater seismic velocity explained

Why then was the average speed of the surface waves recently observed considerably higher than would be expected based on the earlier point measurement under the Mars InSight lander? Is this mainly due to the surface rock, or are other mechanisms in play? In general, volcanic rocks tend to exhibit higher seismic velocities than sedimentary rocks. Also, the paths between the two meteorite impacts and the measurement site pass through one of the largest volcanic regions in Mars’ northern hemisphere.

Lava flows and the closure of pore spaces from heat created by volcanic processes can increase the velocity of seismic waves. “On the other hand, the crustal structure beneath InSight’s landing site may have been formed in a unique way, perhaps when material was ejected during a large meteoritic impact more than three billion years ago. That would mean the structure of the crust under the lander is probably not representative of the general structure of the Martian crust,” Kim explains.

Solving the mystery of the Mars dichotomy

The new research could also help solve a centuries-old mystery. Ever since the first telescopes were pointed at Mars, it has been known that a sharp contrast exists between the planet’s southern and northern hemispheres. While the dominant feature of the southern hemisphere is a plateau covered by meteorite craters, the northern hemisphere consists mostly of flat, volcanic lowlands that may have been covered by oceans in the planet’s early history. This division into southern highlands and northern lowlands is called the Mars dichotomy.

“As things stand, we don’t yet have a generally accepted explanation for the dichotomy because we’ve never been able to see the planet’s deep structure,” says Domenico Giardini, ETH Zurich Professor of Seismology and Geodynamics. “But now we’re beginning to uncover this.” The initial results appear to disprove one of the widespread theories for the Mars dichotomy: the crusts in the north and in the south are probably not composed of different materials, as has often been assumed, and their structure may be surprisingly similar at relevant depths.

A long wait for the wave

The ETH Zurich researchers are expecting further results soon. In May 2022, InSight observed the largest marsquake to date, with a magnitude of 5. It also recorded seismic surface waves generated by this shallow event. This happened just in time since the InSight mission will soon be coming to an end now that the lander’s solar panels are covered in dust, and it is running out of power. An initial analysis of the data confirms the findings that the researchers obtained from the other two meteorite impacts.

“It’s crazy. We’d been waiting for so long for these waves, and now, just months after the meteorite impacts, we observed this big quake that produced extremely rich surface waves. These allow us to see even deeper into the crust, to a depth of about 90 kilometers,” says Kim.

For more on this research, see InSight Mars Lander Detects Stunning Meteoroid Impact on Red Planet.

Reference: “Largest recent impact craters on Mars: Orbital imaging and surface seismic co-investigation” by L. V. Posiolova, P. Lognonné, W. B. Banerdt, J. Clinton, G. S. Collins, T. Kawamura, S. Ceylan, I. J. Daubar, B. Fernando, M. Froment, D. Giardini, M. C. Malin, K. Miljković, S. C. Stähler, Z. Xu, M. E. Banks, É. Beucler, B. A. Cantor, C. Charalambous, N. Dahmen, P. Davis, M. Drilleau, C. M. Dundas, C. Durán, F. Euchner, R. F. Garcia, M. Golombek, A. Horleston, C. Keegan, A. Khan, D. Kim, C. Larmat, R. Lorenz, L. Margerin, S. Menina, M. Panning, C. Pardo, C. Perrin, W. T. Pike, M. Plasman, A. Rajšić, L. Rolland, E. Rougier, G. Speth, A. Spiga, A. Stott, D. Susko, N. A. Teanby, A. Valeh, A. Werynski, N. Wójcicka and G. Zenhäusern, 27 October 2022, Science.
DOI: 10.1126/science.abq7704

NEWS RELATED

EPA blocks mine project that threatened crucial Alaskan salmon runs

The Environmental Protection Agency moved to block the Pebble Mine in Alaska on Tuesday, preventing mining waste discharges into the Bristol Bay watershed. It’s a decision the agency says will preserve the thriving ecosystem and safeguard Alaska’s Sockeye salmon fishery, which produces about half of the world’s harvest of ...

View more: EPA blocks mine project that threatened crucial Alaskan salmon runs

Giant sea scorpion species discovered in New Mexico

Scientists have discovered a giant ancient sea scorpion species in New Mexico that lived between 307 and 303 million years ago. Hibbertopterus lamsdelli was over a metre long and likely lived in a marine-influenced estuary fed by a river delta, according to a new study published in the journal ...

View more: Giant sea scorpion species discovered in New Mexico

Tyre Nichols' death has reignited the debate around police brutality. Here are 5 proven ways to reduce it - and 2 strategies that don't work.

Business Insider Protesters rally as Philadelphia Police officers and Pennsylvania National Guard soldiers look on, June 1, 2020.AP Photo/Matt Slocum Tyre Nichols, 29, died after he was beaten by police at a traffic stop January 7. Campaign Zero, a police-reform initiative, suggested six ways to reduce police violence. Research ...

View more: Tyre Nichols' death has reignited the debate around police brutality. Here are 5 proven ways to reduce it - and 2 strategies that don't work.

Northern Lights Glimmer in Manitoba Night Sky

A Manitoba-based photographer captured the green glow of the aurora borealis over South Indian Lake on Friday, January 27, as the temperature fell to -23 degrees Fahrenheit (-30 Celsius). Timelapse footage published to Twitter by RJ Roldan shows the northern lights on display as the Canadian region was hit ...

View more: Northern Lights Glimmer in Manitoba Night Sky

Amid high levels of contamination, Puerto Rico town's residents plead for action

SALINAS, Puerto Rico — Shuttered windows are a permanent fixture in Salinas, an industrial town on Puerto Rico’s southeast coast that is considered one of the U.S. territory’s most contaminated regions. For years, toxic ash and noxious chemicals from coal-fired and thermoelectric power plants have enveloped this community, and ...

View more: Amid high levels of contamination, Puerto Rico town's residents plead for action

COVID flashback: Here's how NPR reported on the coronavirus at a turning point

On Jan. 23, 2020, as the coronavirus spread in China, residents of Wuhan, where it was first identified, donned masks to go shopping. The U.S. didn’t officially endorse masks as a preventive measure for the public for a number of weeks. Stringer/Getty Images hide caption toggle caption Stringer/Getty Images ...

View more: COVID flashback: Here's how NPR reported on the coronavirus at a turning point

9 diseases that keep epidemiologists up at night

Thinking about the next pandemic keeps lots of researchers busy. Peter Zelei Images/Getty Images hide caption toggle caption Peter Zelei Images/Getty Images Just three years ago, on Jan. 30, 2020, the head of the World Health Organization made a landmark declaration: A “novel coronavirus” that had first been identified ...

View more: 9 diseases that keep epidemiologists up at night

Women who snore struggle to orgasm, new study suggests

(Getty Images) Woman who snore are more likely to suffer from sexual dysfunctions, according to a new study. Sexual disorders are more common among women who suffer from obstructive sleep apnoea (which can cause loud snoring), insomnia, or circadian rhythm sleep disorder according to a study published in the ...

View more: Women who snore struggle to orgasm, new study suggests

Huge meteorite discovered in Antarctica contains oldest material in solar system

My night in a 'gaming suite' forced me to reckon with the time I spend playing video games

Crowdfunded DNA effort helps identify woman found murdered 50 years ago

Peloton instructor Leanne Hainsby, 35, said she was diagnosed with breast cancer after a doctor told her not to worry about a lump in her breast

ChatGPT creator OpenAI might be training its AI technology to replace some software engineers, report says

Fossilized eggs reveal new secrets about one of the world's largest dinosaurs

Rotation of Earth’s inner core may have slowed, puzzling new discovery suggests

How a good teacher can boost your child's future INCOME: Kids in the most effective reception class earn up to £7,500 more, study finds

Study reveals how you can find out if your cats are about to fight

Scientific journals ban ChatGPT use by researchers to author studies

New blood test could detect Alzheimer’s disease years before diagnosis

Is cannabis the secret to ORGASMS for women? Females who smoke before sex are more likely to climax multiple times, study suggests

OTHER NEWS