24. February 2020
First results of the InSight mission and a new plan for the Mars 'Mole'

Seis­mic ac­tiv­i­ty on Mars re­sem­bles that found in the Swabi­an Ju­ra

Cerberus Fossae, shaped by volcanism and tectonics
Cer­berus Fos­sae, shaped by vol­can­ism and tec­ton­ics
Image 1/8, 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 locates marsquakes in the Cerberus Fossae region
In­Sight lo­cates marsquakes in the Cer­berus Fos­sae re­gion
Image 2/8, Credit: NASA/USGS/MOLA; DLR (nach Giardini et al., 2020)

InSight locates marsquakes in the Cerberus Fossae region

The SEIS seis­mome­ter on NASA’s In­Sight lan­der record­ed a to­tal of 174 low-in­ten­si­ty marsquakes be­tween Febru­ary and the end of Septem­ber 2019. With the help of mod­els of the prop­a­ga­tion of seis­mic waves in the Mar­tian sub­sur­face, the prob­a­ble source of two larg­er quakes (s0235b and s0173a) could be de­ter­mined quite ac­cu­rate­ly, and of that an­oth­er quake (s0183a), which pro­duced few­er clear sig­nals, with some­what re­duced ac­cu­ra­cy. The marsquakes oc­curred in the Cer­berus Fos­sae re­gion, a young vol­canic area about 1700 kilo­me­tres east of the In­Sight land­ing site lo­cat­ed in Ely­si­um Plani­tia. Red lines show known fault zones. The to­po­graph­i­cal map is based on laser al­ti­tude mea­sure­ments per­formed by NASA’s Mars Glob­al Sur­vey­or space­craft (1999-2006) and shows height dif­fer­ences from ap­prox­i­mate­ly mi­nus 3000 me­tres (blue-green) to plus 7000 me­tres (sum­mit of Ely­si­um Mons), re­lat­ed to a ref­er­ence sur­face re­ferred to as an areoid. This is a mod­elled el­lip­ti­cal sur­face of equal grav­i­ta­tion­al at­trac­tion, which is used on Mars as a ‘ze­ro’ lev­el in the ab­sence of sea lev­el.
Model of the subsoil conditions
Mod­el of the sub­soil con­di­tions
Image 3/8, Credit: ©IPGP/Nicolas Sarter

Model of the subsoil conditions

The ground at the In­Sight land­ing site con­sists of three dif­fer­ent lay­ers and ma­te­ri­als with dif­fer­ent prop­er­ties. A mod­el of the soil prop­er­ties has been de­vel­oped us­ing the prop­a­ga­tion times of marsquake waves and the sig­nals gen­er­at­ed by the 'Mole' when it was ham­mer­ing in­to the ground with the Heat Flow and Phys­i­cal Prop­er­ties Pack­age (HP3) geother­mal mea­sure­ment sys­tem, as well as the many mea­sure­ments per­formed with the Aux­il­iary Pay­load Sen­sor Suite (APSS) – con­sist­ing of a barom­e­ter, an anemome­ter, a mag­ne­tome­ter and two cam­eras), the HP3 ra­diome­ter and the Ro­ta­tion and In­te­ri­or Struc­ture Ex­per­i­ment (RISE). Be­neath what is re­ferred to as the 'duri­crust' (from Latin 'du­rus', mean­ing hard, and 'crus­ta', mean­ing shell or crust), there is a com­par­a­tive­ly firm crust con­sist­ing of a kind of 'ce­ment­ed' sand and rough­ly com­pa­ra­ble to the firm, caramelised sug­ar crust of a crème brûlée. Fur­ther down, there is a sev­er­al-me­tre-thick re­golith of fine­ly frag­ment­ed crustal rock and fi­nal­ly frag­ment­ed bedrock reach­ing deep un­der­ground.
Quake measurements at night-time
Quake mea­sure­ments at night-time
Image 4/8, Credit: DLR (CC BY-NC-ND 3.0)

Quake measurements at night-time

A day on Mars, a 'sol', lasts 24 hours and 37 min­utes, al­most the same length as a day on Earth. The graph­ic shows a 24-hour clock with Mar­tian hours, which are there­fore slight­ly longer than ter­res­tri­al hours. Mid­night is at the top, fol­lowed clock­wise by morn­ing with sun­rise, noon and evening with sun­set. The slight­ly curved or­ange line in­di­cates the times of sun­rise and sun­set, which vary slight­ly through­out the year. The dis­tance from the cen­tre in­di­cates the num­ber of sols since In­Sight's land­ing. The in­ner­most cir­cle is Sol 72, when the seis­mome­ter be­gan to record con­tin­u­ous­ly. The dif­fer­ent sym­bols show the var­i­ous types of marsquakes, which have dif­fer­ent sig­nal fre­quen­cies. Since the weath­er be­comes no­tice­ably calmer af­ter sun­set, the first half of the night is the best time win­dow for record­ing dis­tant marsquakes, be­cause prac­ti­cal­ly no wind in­ter­feres with the mea­sure­ments be­ing per­formed by the ul­tra-sen­si­tive ex­per­i­ment.
SEIS experiment for recording marsquakes
SEIS ex­per­i­ment for record­ing marsquakes
Image 5/8, Credit: NASA/JPL-Caltech/CNES/IPGP

SEIS experiment for recording marsquakes

The Seis­mic Ex­per­i­ment for In­te­ri­or Struc­ture (SEIS) in­stru­ment is a seis­mome­ter for mea­sur­ing move­ments in the Mar­tian soil at dif­fer­ent fre­quen­cies and con­sists of a to­tal of six sen­sors. The in­stru­ment was de­vel­oped un­der the lead­er­ship of the French space agen­cy CNES. The heart of the SEIS ex­per­i­ment con­sists of two sets of three ex­treme­ly sen­si­tive pen­du­lums that reg­is­ter even the small­est move­ments of the Mar­tian sur­face. The biggest prob­lem for re­li­able mea­sure­ments on Mars is the large tem­per­a­ture dif­fer­ences be­tween day and night and be­tween sum­mer and win­ter. Be­cause ma­te­ri­als ex­pand when warm and con­tract when cold, SEIS is equipped with a so­phis­ti­cat­ed ther­mal pro­tec­tion sys­tem in the form of sev­er­al in­su­lat­ed shells – com­pa­ra­ble to a ‘Ma­tryosh­ka doll’. These cov­ers com­pen­sate for the tem­per­a­ture dif­fer­ences so that the in­stru­ment has sta­ble mea­sure­ment con­di­tions. SEIS is pro­tect­ed from the ef­fects of the Mar­tian wind and the dust trans­port­ed with it by a hemi­spher­i­cal dome con­sist­ing of sev­er­al sep­a­rate lay­ers.
Next activity with the DLR HP³ geothermal sensor system
Next ac­tiv­i­ty with the DLR HP³ geother­mal sen­sor sys­tem
Image 6/8, Credit: NASA/JPL-Caltech

Next activity with the DLR HP³ geothermal sensor system

So far, it has not been pos­si­ble to use the self-ham­mer­ing 'Mole', the main com­po­nent of the DLR Heat Flow and Phys­i­cal Prop­er­ties Pack­age (HP3), to pen­e­trate deep­er than 38 cen­time­tres in­to the Mar­tian soil, which has un­usu­al prop­er­ties, even for Mars. Af­ter the Mole was al­most com­plete­ly in the Mar­tian soil, it backed out a short dis­tance. Sub­se­quent­ly, with re­peat­ed lat­er­al pres­sure from the robot­ic arm, it has moved a lit­tle deep­er in­to the ground, again with a re­cent slight back­ward move­ment. In the com­ing weeks, pres­sure from above with the robot­ic arm should help.
Daily temperature variations at the InSight landing site
Dai­ly tem­per­a­ture vari­a­tions at the In­Sight land­ing site
Image 7/8, Credit: DLR

Daily temperature variations at the InSight landing site

The tem­per­a­ture vari­a­tions on Mars are much greater than on Earth. In­Sight mea­sures the ther­mal ra­di­a­tion at the land­ing site from the ground and from the lay­er of air above us­ing the RAD ra­diome­ter, part of the DLR HP3 ex­per­i­ment. Lo­cat­ed near the equa­tor, the high-el­e­va­tion Sun heats the fine sand on the sur­face to above ze­ro de­grees Cel­sius on most days, while the thin at­mo­sphere re­mains 10 to 20 de­grees Cel­sius cold­er. At night, how­ev­er, tem­per­a­tures drop to mi­nus 90 de­grees Cel­sius or even low­er. The gaps in the tem­per­a­ture curves are due to the fact that, be­cause the op­er­at­ing modes are tai­lored to the ex­per­i­ment and op­ti­mised for the mea­sure­ment of large tem­per­a­ture vari­a­tions, it is not pos­si­ble to mea­sure dur­ing the switch from high to low tem­per­a­ture mode.
NASA's InSight lander on Mars
NASA's In­Sight lan­der on Mars
Image 8/8, Credit: NASA/JPL-Caltech

NASA's InSight lander on Mars

Af­ter its launch on 5 May 2018, NASA's In­Sight space­craft land­ed on 26 Novem­ber of the same year in Ely­si­um Planum, four-and-a-half de­grees north of the equa­tor and 2613 me­tres be­low the ref­er­ence lev­el on Mars. In­Sight, a NASA Dis­cov­ery Class mis­sion, is the first pure­ly geo­phys­i­cal ob­ser­va­to­ry on an­oth­er ce­les­tial body. In ad­di­tion to the French Seis­mic Ex­per­i­ment for In­te­ri­or Struc­ture SEIS (low­er left) and the geother­mal probe HP3 (Heat Flow and Phys­i­cal Prop­er­ties Pack­age, low­er right) pro­vid­ed by DLR, a col­lec­tion of sup­port­ing in­stru­ments are in­stalled on the lan­der plat­form (the Aux­il­iary Pay­load Sen­sor Suite (APSS) – con­sist­ing of a barom­e­ter, an anemome­ter, a mag­ne­tome­ter and two cam­eras), the HP3 ra­diome­ter and the Ro­ta­tion and In­te­ri­or Struc­ture Ex­per­i­ment (RISE).
  • The SEIS experiment on board NASA's InSight geophysical station recorded 174 seismic events up to the end of September 2019.
  • Weak earthquakes – magnitude less than three to four.
  • Accompanying measurements provide information about the local weather conditions.
  • In the coming weeks, the Mars 'Mole' is to be assisted more effectively by pressure from above applied with the robotic arm.
  • Focus: Space, exploration, planetary geophysics

Mars is a seismically active planet – quakes occur several times a day. Although they are not particularly strong, they are easily measurable during the quiet evening hours. This is one of many results of the evaluation of measurement data from the NASA InSight lander, which has been operating as a geophysical observatory on the surface of Mars since 2019. A series of six papers have now been published in the scientific journals Nature Geoscience and Nature Communications. Eight scientists from the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) have made contributions to these. The papers describe the weather and atmospheric dynamics at the landing site, its geological environment, the structure of the Martian crust and the nature and properties of the planetary surface.

The Seismic Experiment for Interior Structure (SEIS) instrument – a seismometer developed by an international consortium under the leadership of the French space agency CNES – recorded a total of 174 seismic events between February and September 2019. Twenty of these marsquakes had a magnitude of between three and four. Quakes of this intensity correspond to weak seismic activity of the kind that occurs repeatedly on Earth in the middle of continental plates, for example in Germany on the southern edge of the Swabian Jura hills. Although only one measurement station is available, models of wave propagation in the Martian soil have been used to determine the probable source of two of these quakes. It is located in the Cerberus Fossae region, a young volcanic area approximately 1700 kilometres east of the landing site.

"Due to the higher gravity, SEIS could only be tested to a limited extent on Earth. We are all very excited about how sensitive it actually is," says Martin Knapmeyer, a geophysicist at the DLR Institute of Planetary Research, who is involved in SEIS data evaluation. "The seismic activity observed on Mars so far is significantly stronger than that found on the Moon – which is what we expected. How much stronger it actually is and whether there are more powerful marsquakes than those of magnitude four will become clear as the mission continues." However, even now, important and fundamentally new conclusions can be drawn about the planet's internal structure: "Similar to the Moon, the crust seems to be heavily disrupted down to a depth of several kilometres. Nevertheless, the seismic signals are more similar to Earth than to the Moon, but we do not yet understand why. For example, much of the time we cannot identify the cause of the marsquakes. Here, we are breaking new scientific ground." The mission will continue at least until the end of 2020 and will continuously provide further data. "We have not detected any meteorite impacts yet. However, it was clear early on that only expect a very small number of impacts would be expected during the mission."

InSight takes the 'pulse' of the Red Planet

This is the first time that an experiment to record marsquakes has provided such data on a larger scale and over a longer period of time. After the Moon, Mars is only the second celestial body other than Earth on which natural quakes have been recorded. It is true that instruments for performing seismic measurements were also installed on the first landers to visit Mars – the legendary Viking 1 and 2 missions – which arrived there in July 1976. However, these instruments were located on the lander platforms and only provided 'noisy' results, which were not particularly meaningful due to the presence of interfering signals, particularly those caused by the wind.

Following its launch on 5 May 2018, InSight landed on 26 November of the same year in Elysium Planum, four-and-a-half degrees north of the equator and 2613 metres below the reference level on Mars. The InSight team named the landing site ‘Homestead hollow’. More precisely, the landing site is located in an old, shallow crater that is approximately 25 metres across. The crater is heavily eroded and filled with sand and dust. The more distant surroundings of InSight are not very interesting geologically, but that was exactly one of the most important criteria for the selection of the landing site. It needed to be flat and level – and have as few rocks and stones as possible. The entire region consists of lava flows that solidified two-and-a-half billion years ago and were subsequently broken down by meteorite impacts and weathering into what is referred to as 'regolith'. It is thought that there are no large boulders down to a depth of at least three metres.

Magnetic field surprise

InSight, a NASA Discovery-class mission, is the first purely geophysical observatory on another celestial body in the Solar System. Its primary objective is to study the composition and structure of Mars, its thermal evolution and current internal state, and current seismic activity. Forces and energies inside a planetary body 'control', to some extent, geological processes – the results of which are visible on the surface – such as volcanism and tectonic fractures in the rigid crust, over billions of years.

With SEIS and the DLR Heat Flow and Physical Properties Package (HP3) geothermal sensor system, together with a collection of supporting instruments (the Auxiliary Payload Sensor Suite (APSS) – consisting of a barometer, an anemometer, a magnetometer, and two cameras), the HP3 radiometer and the Rotation and Interior Structure Experiment (RISE), InSight takes the 'pulse' of the Red Planet, measuring irregularities in its daily rotation and recording atmospheric parameters and weather at the landing site. One surprising result has been the local detection of a magnetic field that is 10 times stronger than predicted using the results of observations from Mars' orbit. This magnetic field is generated by magnetised minerals in the rock. The magnetisation ultimately came from a planet-wide magnetic field from Mars' early history.

The 'moving' day of a seismometer on Mars

Before the turn of the year 2018/2019, the SEIS experiment was set down on the surface of Mars and, protected from wind and weather by its characteristic dome (resembling a 'Cheese Bell') and perfectly horizontally aligned by a levelling system developed at the Max Planck Institute for Solar System Research in Göttingen, started routine measurement operations in February 2019. The experiment is so sensitive that almost any small change at the landing site is recorded as a signal: Movements of the robot arm, gusts of wind, thermal 'stress' in the lander caused by temperature differences, or of course the vibrations of the hammering Mars Mole right beside it. For this reason, the daily weather patterns, in particular the activity of the wind and the extreme fluctuations in temperature in the day and night rhythm, as well as the vibrations caused by the hammering mechanism of the DLR experiment HP3 were analysed.

"We are dealing with much greater temperature differences at the landing site than those that occur on Earth," explains Nils Müller from the DLR Institute of Planetary Research, who has analysed thermal radiation from the surface using the HP3 radiometer experiment. "At midday, the Sun heats the fine sand on the surface to above zero degrees Celsius on most days, while the thin atmosphere remains 10 to 20 degrees Celsius colder. At night, however, temperature drops to minus 90 degrees Celsius or even lower."

During the day, the increase in temperature always results in a very characteristic weather pattern, with winds first freshening and then easing in the afternoon. The scientists have even identified traces of small tornadoes or 'dust devils', frequent phenomena in the Martian weather pattern, on the ground after their course was recorded from orbit by NASA's Mars Atmosphere and Volatile Evolution (MAVEN) orbiter. These dust devils can even raise the Martian soil a little, which is registered by the seismometer. This allows conclusions to be drawn about the properties of the upper layer of the surface material. At night, the weather calms down noticeably, so the best time window for recording distant marsquakes is in the first half of the night, because almost no atmosphere-induced noise interferes with the experiment.

HP3 delivers results and the Mars mole gets help from above

Measurements and observations performed by DLR's HP3 experiment have also been incorporated into the scientific inventory, including the radiometer data and the soil properties derived from the course of the experiment to date, with the hammering of the Mars Mole serving, among other things, as a seismic source for analysing the upper layer of the soil. However, it has not yet been possible to use the self-hammering thermal probe to penetrate deeper than 38 centimetres into the Martian soil there, with its unusual properties, even for Mars. In autumn 2019, the experiment seemed to be well on its way – the 'Mole' was given lateral support by the scoop on the robotic arm, which provided the friction necessary for driving into the subsurface. "After the Mole was almost completely in the Martian soil, it backed out again a small distance. Subsequently, with repeated lateral pressure from the robotic arm, it has moved a little deeper into the ground again with a recent slight backward movement," explains the Principal Investigator of the HP3 experiment – Tilman Spohn from the DLR Institute of Planetary Research. "In the coming weeks we want to help more effectively by applying pressure from above with the scoop on the robotic arm." For months, DLR researchers and numerous technicians and engineers at the Jet Propulsion Laboratory (JPL) have been working meticulously with the Mole on Mars and with simulations, models and tests on Earth to find a solution. In his P.I. blog, Tilman Spohn explains the current situation and the possibilities for moving deeper into the soil with the Mars Mole.

The publications

  • Banerdt, Smrekar et al. (2020) Initial results from the InSight mission on Mars, Nature Geoscience, in press, DOI : 10.1038/s41561-020-0544-y
  • Lognonné et al. (2020) Constraints on the shallow elastic and anelastic structure of Mars from InSight seismic data, Nature Geoscience, in press, DOI : 10.1038/s41561-020-0536-y
  • Giardini et al. (2020) The seismicity of Mars, Nature Geoscience, in press, DOI : 10.1038/s41561-020-0539-8
  • Banfield, Spiga et al. (2020) The atmosphere of Mars as observed by InSight, Nature Geoscience, in press, DOI : 10.1038/s41561-020-0534-0
  • Johnson et al. (2020) Crustal and time-varying magnetic fields at the InSight landing site on Mars, Nature Geoscience, in press, DOI : 10.1038/s41561-020-0537-x
  • Golombek et al. (2020) Geology of the InSight Landing Site on Mars, Nature Communications, in press, DOI : 10.1038/s41467-020-14679-1

The HP3 instrument on NASA's InSight mission

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. DLR is contributing the Heat Flow and Physical Properties Package (HP3) experiment to the mission. The scientific leadership lies with the DLR Institute of Planetary Research, which was also in charge of developing and implementing the experiment in collaboration with the DLR Institutes of Space Systems, Optical Sensor Systems, Space Operations and Astronaut Training, Composite Structures and Adaptive Systems, and System Dynamics and Control, as well as the Institute of Robotics and Mechatronics. Participating industrial partners are Astronika and the CBK Space Research Centre, Magson GmbH and Sonaca SA, the Leibniz Institute of Photonic Technology (IPHT) as well as Astro- und Feinwerktechnik Adlershof GmbH. Scientific partners are the ÖAW Space Research Institute at the Austrian Academy of Sciences and the University of Kaiserslautern. The DLR Microgravity User Support Center (MUSC) in Cologne is responsible for HP3 operations. In addition, the DLR Space Administration, with funding from the German Federal Ministry for Economic Affairs and Energy, supported a contribution by the Max Planck Institute for Solar System Research to the French main instrument SEIS (Seismic Experiment for Interior Structure).

Detailed information on the InSight mission and the HP3 experiment is available on DLR's dedicated mission site, with extensive background articles. Information can also be found in the animation and brochure about the mission or via the hashtag #MarsMaulwurf on the DLR Twitter channel. Tilman Spohn, the Principal Investigator for the HP3 experiment, is also providing updates in the DLR Blog portal about the activities of the Mars Mole.

  • Falk Dambowsky
    Ger­man Aerospace Cen­ter (DLR)

    Com­mu­ni­ca­tions and Me­dia Re­la­tions
    Telephone: +49 2203 601-3959
    Linder Höhe
    51147 Cologne
  • Prof.Dr. Tilman Spohn
    HP³ Prin­ci­pal In­ves­ti­ga­tor
    Ger­man Aerospace Cen­ter (DLR)

    DLR In­sti­tute of Plan­e­tary Re­search
    Telephone: +49 30 67055-300
    Fax: +49 30 67055-303
    Linder Höhe
    51147 Köln
  • Matthias Grott
    Ger­man Aerospace Cen­ter (DLR)
    In­sti­tute of Plan­e­tary Re­search, Plan­e­tary Geodesy
    Telephone: +49 30 67055-419

  • Martin Knapmeyer
    Ger­man Aerospace Cen­ter (DLR)
    In­sti­tute of Plan­e­tary Re­search
    Telephone: +49 30 67055-394
    Rutherfordstraße 2
    12489 Berlin
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