27. October 2022
Marsquakes and chunks of ice

Me­te­orite im­pact pro­vides a glimpse be­neath Mars' sur­face

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Space
New impact crater with ice chunks on Mars
New im­pact crater with ice chunks on Mars
Image 1/5, Credit: NASA/JPL-Caltech/University of Arizona

New impact crater with ice chunks on Mars

Chunks of wa­ter ice can be seen around the rim of the new­ly formed im­pact crater on Mars. The 150-me­tre crater was formed on 24 De­cem­ber 2021 by a me­te­orite im­pact in the Ama­zo­nis Plani­tia re­gion. The im­age was ac­quired by the HiRISE cam­era on board NASA's Mars Re­con­nais­sance Or­biter.
The planet Mars
The plan­et Mars
Image 2/5, Credit: NASA/JPL/MSSS

The planet Mars

Mars's di­am­e­ter is on­ly about half the size of our plan­et and its mass is one third the mass of the Earth. It is sur­round­ed by a thin at­mo­sphere of car­bon diox­ide, which con­dens­es in­to ice crys­tals at the plan­et's high vol­ca­noes and forms cir­rus clouds. Mars' north and south poles are cov­ered by ice caps that grow and shrink sea­son­al­ly.
Meteorite impact on Mars
Me­te­orite im­pact on Mars
Image 3/5, Credit: © DLR. All rights reserved

Meteorite impact on Mars

On 24 De­cem­ber 2021, the French seis­mome­ter SEIS (Seis­mic Ex­per­i­ment for In­te­ri­or Struc­tures) record­ed a mag­ni­tude 4 earth­quake at the geo­phys­i­cal sta­tion In­Sight (yel­low star). When eval­u­at­ing the seis­mo­gram, the SEIS sci­ence team de­ter­mined that the marsquake was caused by the im­pact of a large me­te­orite. It was al­so pos­si­ble to re­con­struct the epi­cen­tre of 'Event S1094', the Ama­zo­nis Plani­tia plain north­west of Olym­pus Mons, the largest vol­cano on Mars. Im­ages from NASA's Mars Re­con­nais­sance Or­biter re­vealed the new mar­tian crater about 3600 kilo­me­tres from In­Sight. It has a di­am­e­ter of 150 me­tres and is 21 me­tres deep. It is the first time that a quake re­sult­ing from a me­te­orite or as­ter­oid im­pact has been record­ed on an­oth­er ce­les­tial body and that the lo­ca­tion of the im­pact was sub­se­quent­ly re­con­struct­ed and found.
Cerberus Fossae, shaped by volcanism and tectonics
Cer­berus Fos­sae, shaped by vol­can­ism and tec­ton­ics
Image 4/5, Credit: ESA/DLR/FU Berlin

Cerberus Fossae, shaped by volcanism and tectonics

The land­scape in the Cer­berus Fos­sae re­gion seems to have been cut by a knife. The tec­ton­ic frac­ture struc­tures were formed less than 100 mil­lion years ago, per­haps as re­cent­ly as 10 mil­lion years ago. This can al­so be seen in the pro­file of the fos­sae, which are bor­dered by ex­treme­ly steep walls, al­most ver­ti­cal in places and more than 500 me­tres tall in places, which have hard­ly been flat­tened by ero­sion. The SEIS seis­mome­ter on NASA's In­Sight mis­sion was able to de­tect two quakes here, about 1700 kilo­me­tres east of the land­ing site, quite ac­cu­rate­ly and an­oth­er with some­what greater un­cer­tain­ty. The im­age was ac­quired on 27 Jan­uary 2018 by the High Res­o­lu­tion Stereo Cam­era (HRSC) on board the Eu­ro­pean Mars Ex­press space­craft.
InSight mission on Mars
In­Sight mis­sion on Mars
Image 5/5, Credit: NASA/JPL-Caltech

InSight mission on Mars

Mod­elled rep­re­sen­ta­tion of NASA's In­Sight geo­phys­i­cal mis­sion at its land­ing site in the Ely­si­um Plani­tia plain near the Mar­tian equa­tor. Two ex­per­i­ments are placed on the Mar­tian soil in front of the plat­form: The French seis­mome­ter SEIS (Seis­mic Ex­per­i­ment for In­te­ri­or Struc­tures) and the Heat Flow and Phys­i­cal Prop­er­ties Pack­age (HP3) de­vel­oped by the Ger­man Aerospace Cen­ter (DLR). In­Sight land­ed on Mars on 26 Novem­ber 2018. SEIS has record­ed a to­tal of 1318 Mars quakes since its de­ploy­ment at the be­gin­ning of 2019.
  • Christmas surprise: Seismometer on NASA's InSight mission registers a marsquake of magnitude 4 on 24 December 2021, which turned out to be a meteorite impact.
  • The impact site has been determined, with images from orbit showing a crater 150 metres in diameter revealing an exposed subterranean layer of ice.
  • Important evidence of different structures, porosity and density of the crust.
  • Focus: Space, exploration, Mars, asteroids

On 24 December 2021, NASA's InSight lander felt the ground shake. Its SEIS seismometer registered a marsquake of magnitude 4. Independently, a 150-metre diameter crater was photographed from orbit by the cameras of the Mars Reconnaissance Orbiter. The camera team was able to determine that it was formed on 24 December, and realised that this was the same day as the reported quake. When the two teams compared notes, they found that the location derived from the seismic data was the same as the crater location and concluded that the seismic signal originated from the impact. This is the first time that a meteorite impact on another planet has been recorded both photographically and seismically. To the surprise of scientists, large amounts of water ice were thrown on to the surface by the impact, officially named S1094b. Two articles published today in the journal Science describe the event and its effects in detail. Researchers from the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) are involved in the analyses. In addition, an article on tectonics on Mars was published in Nature Astronomy at the same time, which explains that the marsquakes observed with InSight in recent years are the result of earlier volcanic activity in the Cerberus Fossae area.

From a seismological perspective, the photographic evidence of the impact makes it possible to determine the exact distance to the epicentre, which could otherwise only be estimated much less precisely with a single seismometer. This makes it possible to more accurately measure the path of the seismic waves through Mars and the properties of the rocks along this path. Observing meteorite impacts thus helps to understand the interior of Mars even better.

When the meteoroid struck, in a region called Amazonis Planitia, it blasted a crater roughly 150 metres across and 21 metres deep into the Martian soil. The dark halo of churned-up material surrounding it measures at least 37 kilometres across. With the seismic detection by InSight and the subsequent images from the Mars Reconnaissance Orbiter, the researchers had the extremely rare good fortune to 'witness' the formation of a crater of this size. Many larger craters exist on the planet but they are several million or billion years old.

Before and after comparison of the impact
Before and after comparison of the impact
The black-and-white camera aboard the Mars Reconnaissance Orbiter captured these before-and-after images of the impact, which occurred on 24 December 2021 in the Amazonis Planitia region on Mars.
Credit: NASA/JPL-Caltech/MSSS

Ice beneath the surface near the Martian equator

Brand new craters offer insights into the processes of crater formation, exposing fresh subsurface material that has yet to be modified by wind, weather and sunlight. In this case, large chunks of ice scattered by the impact were captured by NASA's Mars Reconnaissance Orbiter HiRISE (High-Resolution Imaging Science Experiment) colour camera, suggesting that the impact exposed a layer of ice from 10 to 20 metres below the surface. For future crewed Mars missions, it would be particularly beneficial to see where subsurface ice for human use can be found on Mars: subsurface water ice has been spotted several times in the northern lowlands, but never so close to the Martian equator, where Mars is warmest.

Second impact discovered in seismic data

After examining the seismic signal of the impact, the research team also revisited older data to look for similar seismograms. The data revealed that the epicentre of a quake that had occurred on 18 September 2021 also corresponded to a fresh crater of more than 100 metres in diameter. This impact is also described in the study. "It's unprecedented to find a fresh impact of this size," said Ingrid Daubar of Brown University, who leads InSight’s Impact Science Working Group. "It's an exciting moment in geologic history, and we got to witness it."

Surface waves provide conclusions about Martian crust

The quake triggered by this massive impact in December 2021 was the first observed by the mission to involve surface waves – a type of seismic wave that propagates along the top of the planet's crust. The second of two papers published today in the journal Science describes how scientists used these waves to study the structure of Mars' crust. "The analyses of the two impact events show that the crustal structure on the respective route from the impact to the InSight platform differs from the crustal structure at the landing site itself," explains Ana-Catalina Plesa. "The higher average propagation velocities of the seismic waves indicate a different composition of the crust in these areas. A lower porosity of the crust there could also be a cause. Both, in turn, would indicate a higher crustal density and local variations in the density of the Martian crust that we have not seen before." Preliminary analyses suggest that the crustal structure of the northern and southern Martian hemispheres may be similar at depths ranging between five and 30 kilometres. "Further analyses and direct comparison of seismic waves from both impact events will give us important clues about the formation and expression of the 'Martian dichotomy', which describes the division between the northern lowlands and southern highlands on Mars," Plesa added.

Many marsquakes provide clues to Mars tectonics

In another recent publication in the journal Nature Astronomy, the marsquake recorded over the past three years have been put into a geological context: Most of the quakes for which an epicentre could be calculated occurred in the Cerberus Fossae area, about 1500 kilometres east of InSight’s location. This is a relatively young volcanic centre, with the last eruptions occurring around 50,000 to 200,000 years ago. "A striking feature of Cerberus Fossae are grabens hundreds of kilometres long but very narrow and deep, running through the landscape like cracks in a rising dough," explains seismologist Martin Knapmeyer from the DLR Institute of Planetary Research, who is involved in this study. "Such graben are created when volcanic 'veins' form; that is, when magma from greater depths penetrates cracks in the upper crust, causing the entire region to bulge and rise. Over time, the magma solidifies and contracts somewhat in the process. Some of the recorded marsquakes took place at locations close to the last ejected lava and some just below the visible graben. This shows seismograms that fit well with cooling gangue rocks," added Knapmeyer.

Another 'family' of marsquake, on the other hand, shows an unusually slow fracture propagation, as is known from volcanic areas on Earth, such as the Eifel. This slow fracture propagation is related to the heating of the rock by the intruded magma. "Thus, the SEIS data show that Cerberus Fossae also resembles known volcanic areas in Earth's subsurface, and that volcanism there, like in the Eifel, is perhaps not yet completely extinct, but is currently only dormant," Knapmeyer emphasises.

InSight's final selfie
InSight's final selfie
NASA's InSight Mars lander took this last selfie on 24 April 2022, the 1211 Martian day (sol) of the mission. The lander's solar panels have become covered in dust since landing on Mars in November 2018, leading to a gradual decline in performance.
Credit: NASA/JPL-Caltech

InSight provides a glimpse into the Martian interior

InSight was sent to the Red Planet to study Mars' deep interior – its crust, mantle and core – which can give scientists an insight into the formation of all terrestrial bodies, including Earth and the Moon. Seismic waves are key to this improved understanding. Since InSight's touchdown on November 2018, the SEIS experiment has recorded 1318 marsquakes, including several caused by much smaller meteoroid impacts. Most of the quakes, however, were caused by tectonic tremors, that is, displacements of rock masses like in earthquakes.

The frequency of large meteorite impacts is of interest not only because of the possible danger to future astronauts; the number and size of craters on other planets is used to estimate the age of their surfaces. This statistical evaluation includes the impact frequency, which can be determined more precisely the more impacts can be directly observed. Finally, the recent experiment of the DART mission was aimed at preventing impacts like S1094b on Earth.

The InSight mission is being carried out by NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, on behalf of the agency's Science Mission Directorate. InSight is part of NASA's Discovery Program. The German Space Agency at DLR, with funding from the German Federal Ministry for Economic Affairs and Climate Action, supported a contribution by the Max Planck Institute for Solar System Research to the French main instrument SEIS (Seismic Experiment for Interior Structure). DLR researchers are involved in the evaluation of the SEIS data. In addition, DLR contributed the Heat Flow and Physical Properties Package (HP3) experiment to the mission.

Detailed information on the InSight mission and the HP3 experiment is available on DLR's dedicated mission site.

Contact
  • Falk Dambowsky
    Ed­i­tor
    Ger­man Aerospace Cen­ter (DLR)

    Com­mu­ni­ca­tions and Me­dia Re­la­tions
    Telephone: +49 2203 601-3959
    Linder Höhe
    51147 Cologne
    Contact
  • Martin Knapmeyer
    HP³ and SEIS project sci­en­tist and mem­ber of the In­Sight sci­ence team
    Ger­man Aerospace Cen­ter (DLR)
    In­sti­tute of Plan­e­tary Re­search
    Plan­e­tary Physics
    Rutherfordstraße 2
    12489 Berlin
    Contact
  • Ana-Catalina Plesa
    HP³ project sci­en­tist of the In­Sight sci­ence team, plan­e­tary geo­physics and plan­e­tary mod­elling
    Ger­man Aerospace Cen­ter (DLR)
    In­sti­tute of Plan­e­tary Re­search
    Plan­e­tary Physics
    Rutherfordstraße 2
    12489 Berlin
    Contact
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InSight

On 5 May 2018, NASA's InSight lander launched with a mission to explore Mars' internal structure and heat balance by acquiring geophysical data on the surface. DLR contributed the HP3 (Heat Flow and Physical Properties Package) instrument.