Mysterious magnetic impulses discovered on Mars

At midnight on Mars, the magnetic field of the red planet begins to pulse in a way that has never been observed before. The cause is currently unknown.

This is one of the amazing preliminary discoveries of NASA's first-ever robot geophysicist, the InSight lander. Since landing in November 2018, this spacecraft has been gathering information to help scientists better understand the insides and the evolution of the neighboring planet, such as taking the temperature of its upper crust, recording the sounds of extraterrestrial earthquakes and measure the strength and direction of the planet's magnetic field.

As has been revealed in a handful of presentations this week at a joint meeting of the European Congress of Planetary Science and the American Astronomical Society, early data suggest that the magnetic machinations of Mars are wonderfully crazy.

In addition to the odd magnetic pulses, the LG data show that the Martian crust is much more powerfully magnetic than that expected by scientists. In addition, the LG has detected a very particular electrically conductive layer, about 2.5 miles thick, located below the surface of the planet. It is far too early to say for sure, but it is possible that this layer represents a global reservoir of liquid water.

On Earth, groundwater is a hidden sea enclosed in sand, soil and rocks. If something similar is on Mars, then "we should not be surprised," says Jani Radebaugh, scientist in planetary sciences at Brigham Young University, who did not participate in the work. But if these results are convincing, a liquid region of this magnitude on modern Mars will have enormous consequences on life potential, past or present. (Get the facts about previous evidence for an underground lake on Mars.)

Until now, none of this data has been peer reviewed and the details of initial findings and interpretations will no doubt be fine-tuned over time. Nevertheless, the revelations offer a magnificent showcase to InSight, a robot that could revolutionize our understanding of Mars and other rocky worlds in the galaxy.

"We have a glimpse into the magnetic history of Mars in an unprecedented way," says Paul Byrne, a global geologist at North Carolina State University, who did not participate in this work.

The Earth has a major global magnetic field thanks to its liquid outer core, rich in iron and rotation. We know that this area has existed for some time and that it has evolved considerably from one geological time to another, based on natural recordings of its strength and orientation trapped in minerals specific to the Earth's crust. . The history of the Mars magnetic field is archived in the same way in its crust, as scientists learned in 1997, thanks to data from the Mars Global Surveyor orbiter.

"The same zoo of magnetic minerals existing on Earth exists on Mars," says Robert Lillis, a global space physicist at the University of California at Berkeley, who did not take part in the new research.

The orbiter detected the magnetism of the red planet 60 to 250 km above the surface and found that the magnetic field of the Earth's crust was ten times stronger than that of the Earth when measured at the same altitude. This suggests that once upon a time, Mars, an important global magnetic field.

Unlike Earth, Mars was unlucky. About four billion years ago, its convulsive external core seems to be seized, causing a collapse of its overall magnetic field. Left with a weak magnetic shield to defend itself, a wave of radiation emitted by the sun – known as the solar wind – has gradually stripped a large part of its ancient atmosphere, transforming a world rich in water and potentially vital into a cold desert.

Understanding why these two planets have had such a different destiny requires the best possible measurements of the magnetic ghosts of Mars, but in orbit, the strength of this remaining magnetic field has a low resolution. It's like watching a crowd of people from afar: if many wear red shirts and some wear blue, a distant camera will largely record the preponderance of red. But get closer with the same camera and you will see more clearly these blue shades so important.

"The same goes for magnetic measurements," says Dave Brain, a research scientist in the atmosphere and space physics of the University of Colorado, not involved in the work. "The closer you get, the more you can choose a structure."

The InSight magnetometer, the first placed on the Martian surface, gave scientists their best look at the magnetic field of the crust and gave them a shock: the magnetic field near the robot was about 20 times more powerful than what had been predicted on past orbital measurements.

Brain, who is familiar with the InSight data, claims that this powerful and stable magnetic signal comes from rocks close to InSight, but that it is difficult to determine whether it is underground depths. or closer to the surface. This identification is important, says Byrne, because if it came from younger rocks near the surface, this would imply that a strong magnetic field persists around Mars longer than we currently think.

Perhaps even more intriguing, InSight also discovered that the magnetic field of the Earth's crust near its location was shaking from time to time. This wobbling is known as magnetic pulsation, says Matthew Fillingim, a space physicist at the University of California at Berkeley and a member of the InSight science team.

These pulses are fluctuations in the intensity or direction of the magnetic field and they are not quite unusual. Many of them occur on Earth and on Mars, caused among other things by the higher atmospheric chaos, the action of the solar wind and the magnetic folds of the magnetic bubbles of the planets.

What is strange is that these Martian flickering occur at midnight local, as if they met the requirements of an invisible night timer.

InSight is close to the equator of Mars, and in the same geographical position on Earth, at this time of night, you do not see these types of magnetic pulses. Nighttime pulsations on Earth tend to occur at higher latitudes and are related to north and south lights. At present, sources on Mars do not have a clear source, but scientists have at least one suspect in mind.

Although it has no more powerful global magnetic field, Mars is surrounded by a weak magnetic bubble created by the interaction of the solar wind with its fine atmosphere. This bubble is in turn compressed by the magnetic field of the solar wind, so that part of the bubble takes the form of a tail. At midnight, the InSight spot on Mars is aligned with this tail, and when it passes through, the tail can pinch the magnetic field at the surface like a guitar string.

If a high altitude spacecraft, such as Mars Atmosphere and Evolution Volatile, or MAVEN, the orbiter, NASA can rock over InSight at the right time, this could be the proof. For now, it's a puzzle without answers.

In one of the Mars magnetism presentations, scientists also indicated that the characteristics of the magnetic signals appeared to record an electrically conductive layer somewhere below the Martian surface. Although the team can not yet determine the exact depth, she thinks the depth will not be less than 62 miles.

Trials in deserts on Earth have shown how magnetometers can tell you when there is deep water, says Brain. The same applies to the InSight magnetometer, and it is possible that the layer it has spotted is a water aquifer containing dissolved solids, or a layer of ice and water, which could expand all over the planet.

It is not known how long the surface water bodies have persisted in the lakes, rivers and even oceans of Mars' past, but there is some evidence that the basement now contains salt reservoirs . The Mars crust is also warming as you go, says Radebaugh. And given the strong evidence of ground ice on Mars, it is reasonable to assume that underground aquifers of liquid water also exist.

But the devil is in the details, and all the other causes of such a signal have yet to be eliminated, says Brain. The InSight lander has a drill, but it can dig only about 16 feet below the surface. Scientists may need to find other ways, perhaps through future missions on Mars, to test the theory of the aqueous layer.

If the existence of this Martian aquifer is finally verified or questioned, adds Brain, the invaluable nature of the InSight measures, including its magnetic measurements, is already evident. Even rooted in one place in Elysium Planitia, this robotic emissary begins to unearth all sorts of hidden Martian wonders.