Mysterious magnetic pulses discovered on Mars

The nighttime events are among initial results from the InSight lander, which also found hints that the red planet may host a global reservoir of liquid water deep below the surface.

The InSight lander sits on the Martian surface in an illustration. Preliminary data from the lander's magnometer suggest that the red planet's magnetic field wobbles in inexplicable ways at night.

At midnight on Mars, the red planet’s magnetic field sometimes starts to pulsate in ways that have never before been observed. The cause is currently unknown.

That’s just one of the stunning preliminary findings from NASA’s very first robotic geophysicist there, the InSight lander. Since touching down in November 2018, this spacecraft has been gathering intel to help scientists better understand our neighboring planet’s innards and evolution, such as taking the temperature of its upper crust, recording the sounds of alien quakes, and measuring the strength and direction of the planet’s magnetic field.

As revealed during a handful of presentations this week at a joint meeting of the European Planetary Science Congress and the American Astronomical Society, the early data suggest the magnetic machinations of Mars are marvelously mad.

How NASA's next Mars mission will take the red planet's pulse

In addition to the odd magnetic pulsations, the lander’s data show that the Martian crust is far more powerfully magnetic than scientists expected. What’s more, the lander has picked up on a very peculiar electrically conductive layer, about 2.5 miles thick, deep beneath the planet’s surface. It’s far too early to say with any certainty, but there is a chance that this layer could represent a global reservoir of liquid water.

On Earth, groundwater is a hidden sea locked up in sand, soil, and rocks. If something similar is found on Mars, then “we shouldn’t be surprised,” says Jani Radebaugh, a planetary scientist at Brigham Young University who was not involved with the work. But if these results bear out, a liquid region at this scale on modern Mars has enormous implications for the potential for life, past or present. (Get the facts about previous evidence for an underground lake on Mars.)

So far, none of these data have been through peer review, and details about the initial findings and interpretations will undoubtedly be tweaked over time. Still, the revelations provide a stunning showcase for InSight, a robot that has the potential to revolutionize our comprehension of Mars and other rocky worlds across the galaxy.

“We’re getting an insight into Mars’s magnetic history in a way we’ve never had before,” says Paul Byrne, a planetary geologist at North Carolina State University who was not involved with the work.

A tale of two worlds

Earth has a major global magnetic field thanks to its rotation and churning, iron-rich, liquid outer core. We know that this field has been around for a while and that it has shifted about fairly dramatically across geological epochs, based on natural records of its strength and direction trapped in specific minerals within the crust. The history of Mars’s magnetic field is similarly archived in its crust, as scientists learned in 1997 thanks to data from the Mars Global Surveyor orbiter.

“The same zoo of magnetic minerals that exist on Earth exist on Mars,” says Robert Lillis, a planetary space physicist at the University of California, Berkeley, who wasn’t involved with the new research.

The orbiter detected the red planet’s magnetism from 60 to 250 miles above the surface, and it found that the crustal magnetic field is ten times stronger than Earth’s is when measured from the same height above the surface. This suggests that, once upon a time, Mars also had a major global magnetic field.

Unlike Earth, though, Mars got unlucky. Around four billion years ago, its convulsing outer core appears to have seized up, causing a collapse in its global magnetic field. Left with a weak magnetic shield to defend itself, an outpouring of radiation from the sun—known as the solar wind—gradually stripped away much of its ancient atmosphere, turning a potentially life-supporting, water-rich world into a cold desert.

Grasping why these two planets had such different fates requires the best possible measurements of Mars’ magnetic ghosts, but from orbit, the strength of this remnant magnetic field has poor resolution. It’s like looking at a crowd of people from far away: If many are wearing red shirts and a few are wearing blue, a camera at a distance will largely register the preponderance of red. But get close with the same camera, and those all-important blue hues will be more clearly seen.

“The same is true for magnetic measurements,” says Dave Brain, a researcher of atmospheric and space physics from the University of Colorado not involved with the work. “The closer you get, the more structure you are able to pick out.”

Mysteries at midnight

InSight’s magnetometer, the first placed on the Martian surface, gave scientists their best look yet at the crustal magnetic field, and it gave them a bit of a shock: The magnetic field near the robot was around 20 times stronger than what had been predicted based on past orbital measurements.

Brain, who is familiar with the InSight data, says that this strong, stable magnetic signal is coming from rocks near InSight, but whether they are deep underground or nearer to the surface is currently unclear. That identification matters, Byrne says, because if it’s coming from younger rocks near the surface, it would imply that a strong magnetic field persisted around Mars for longer than we currently think.

We’re getting an insight into Mars’s magnetic history in a way we’ve never had before.
Paul ByrneNorth Carolina State University

Perhaps even more puzzling, InSight also found that the crustal magnetic field near its location jiggled about every now and then. This wobbling is known as a magnetic pulsation, explains Matthew Fillingim, a space physicist at the University of California, Berkeley, and a member of the InSight science team.

These pulses are fluctuations in the strength or direction of the magnetic field, and they are not entirely unusual. Plenty of them happen on Earth and Mars triggered by upper atmospheric chaos, the action of the solar wind, and kinks in the planets’ magnetic bubbles, among other things.

What’s strange is that these Martian wobbles happen at local midnight, as if responding to the demands of an unseen, nocturnal timer.

InSight is near Mars’ equator, and in the same geographic position on Earth, at that time of night, you don’t see these types of magnetic pulsations. Night-time pulsations on Earth tend to happen at higher latitudes and are linked to the northern and southern lights. Right now, the ones on Mars have no clear source, but scientists have at least one suspect in mind.

Although it no longer has a potent global magnetic field, Mars is surrounded by a weak magnetic bubble created as the solar wind interacts with its thin atmosphere. This bubble is in turn compressed by the solar wind’s magnetic field, causing part of the bubble to take on a tail-like shape. At midnight, InSight’s spot on Mars is aligned with this tail, and as it passes through, the tail may be plucking the surface magnetic field like a guitar string.

If a high-altitude spacecraft, like NASA’s Mars Atmosphere and Volatile Evolution, or MAVEN, orbiter, can swing above InSight at just the right time, it might show this to be the case. For now, though, it’s a puzzle without an answer.

Making a splash

During one of the presentations about Mars’ magnetism, scientists also mentioned that features in the magnetic signals appear to be registering an electrically conductive layer somewhere beneath the Martian surface. While the team can’t yet pinpoint an exact depth, they think it wouldn’t be any deeper than 62 miles.

Tests in deserts on Earth have shown how magnetometers are able to tell you whether there is water at depth, Brain explains. The same applies to InSight’s magnetometer, and it is possible that the layer it spotted is an aquifer of water with dissolved solids, or an ice and water layer, that could stretch around the entire planet.

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A self-portrait of the Mars rover Curiosity.

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This field of dunes lies on the floor of an old crater in Noachis Terra, one of the oldest places on Mars.
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This enhanced color image shows several craters somewhere in the southern mid-latitudes of Mars. The bluish deposits are most likely iron-bearing minerals that have not been previously oxidized, or rusted.

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The impact site of the heat shield from NASA's Mars exploration rover Opportunity.

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Sand dunes are among the most widespread aeolian, or wind-blown, features on Mars. These areas provide clues to the sedimentary history of the surrounding terrain.

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Groups of dark brown streaks were photographed by the Mars Reconnaissance Orbiter on melting pinkish sand dunes covered with light frost.

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The panoramic camera on NASA's Mars exploration rover Opportunity captured this scene of the west rim of the Endeavour crater during the summer of 2014.

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Sand dunes litter the floor of Aram Chaos, an eroded impact crater east of Mars's Valles Marineris canyon range.

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Melas Chasma is the widest segment of Valles Marineris, the largest canyon in the solar system.

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The Opportunity rover spent four months perched on the northern slope of Greely Haven and snapped more than 800 images of its surroundings.

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The Russell crater dunes are a favorite target for the Mars Reconnaissance Orbiter's HiRISE camera, not only because of their incredible beauty, but for measuring the accumulation of frost each fall and its disappearance in the spring.

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The holes visible in this image are not impact craters, but rather material that was ejected from a large crater called Hale that does not appear here. Explosions formed moats, which have been partially covered over time by sand dunes (top).

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NASA's Curiosity rover snapped this 360-degree panorama as part of a long-term campaign to document the context and details of the geology and landforms along Curiosity's traverse since landing in 2012.

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Recurring slope lineae (RSL) are seasonal flows on warm slopes and are especially common in central and eastern Valles Marineris.

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Victoria crater has a distinctive "scalloped" shape to its rim, caused by erosion and downhill movement of crater wall material.

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Dust accumulation on a rover's solar panels reduces its power supply, and the rover's mobility is limited until winter is over or wind cleans the panels.

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The Curiosity rover captured the Bagnold Dunes inside Gale crater on September 25, 2015.

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Partially exposed bedrock is exposed within the Koval'sky impact basin.

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This dramatic, fresh impact crater spans approximately 100 feet (30 meters) in diameter and is surrounded by a large, rayed blast zone.

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The north polar layered deposits are layers of dusty ice up to three kilometers (two miles) thick and approximately 1,000 kilometers (620 miles) in diameter.

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Sand dunes are among the most widespread wind-formed features on Mars. Their distribution and shapes are affected by changes in wind direction and wind strength.

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This selfie from NASA's Curiosity rover shows the vehice at the site where it reached down to drill into a rock target called "Buckskin" on lower Mount Sharp.

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Researchers used the Curiosity rover in March 2015 to examine the structure and composition of the crisscrossing veins at the "Garden City" site in the center of this scene.

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This crater near Sirenum Fossae has steep inner slopes carved by gullies.

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This image covers many shallow irregular pits with raised rims, but researchers aren't sure how these odd features formed.

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At this site in the lower mounter in Gale crater, orbiting instruments have detected signatures of both clay minerals and sulfate salts. This change in mineralogy may reflect a change in the ancient environment in Gale crater.

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Viscous, lobate flow features are commonly found at the bases of slopes in the mid-latitudes of Mars and are often associated with gullies.

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Many Martian landscapes contain features that are similar to ones we find on Earth, like river valleys, cliffs, glaciers, and volcanoes.

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Two of the raised treads, called grousers, on the left middle wheel of NASA's Curiosity rover broke during the first quarter of 2017, including the one seen partially detached at the top of the wheel in this image from the camera on the rover's arm.

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In the scenic Murray Buttes area, individual buttes and mesas were assigned numbers. This one is referred to as "M9a."

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This observation from NASA's Mars Reconnaissance Orbiter shows late summer in Mars's southern hemisphere. The sun is low in the sky, highlighting the subtle topography.

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NASA's Curiosity rover team has assessed the small bright object just below the center of this image and believe it is debris from the spacecraft.

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The High Dune, which is part of the Bagnold Dunes, was the first Martian sand dune ever studied up close. The dunes are active, migrating up to about one yard or meter per year.

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A towering dust devil casts a serpentine shadow over the Martian surface in this stunning late-springtime image of Amazonis Planitia.

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Landforms called "gullies" found on many large Martian sand dunes consist of an alcove, channel, and apron.

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NASA plans to launch another rover to Mars in 2020.

Tap images for captions

It’s unclear how long bodies of surface water persisted in lakes, rivers, and even oceans in Mars’ past, but there is some evidence that the subsurface contains briny reservoirs today. Mars’s crust also gets warmer as you go deeper, Radebaugh says. And given the strong evidence for widespread ground ice on Mars, it is reasonable to think that subterranean aquifers of liquid water exist, too.

But the devil is in the details, and all other causes of such a signal still need to be ruled out, Brain says. The InSight lander has a drill, but it can only dig down about 16 feet below the surface, so scientists may have to find other ways—perhaps via future Mars missions—to test the watery layer theory.

Whether this Martian aquifer’s existence is ultimately verified or rebuffed, Brain adds, the invaluable nature of InSight’s measurements, including its magnetic ones, is already clear. Even rooted to a single spot in Elysium Planitia, this robotic emissary is beginning to dig up all kinds of buried Martian marvels. 

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