When NASA’s Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (Insight) lander set down on Mars in November of 2018, it began its two-year primary mission of studying Mars’ seismology and interior environment. And now, just over a year and a half later, the results of the lander’s first twelve months on the Martian surface have been released in a series of studies.
One of these studies, which was recently published in the journal Nature Geosciences, shared some rather interesting finds about magnetic fields on Mars. According to the research team behind it, the magnetic field within the crater where InSight’s landed is ten times stronger than expected. These findings could help scientists resolve key mysteries about Mars’ formation and subsequent evolution.
These readings were obtained by InSight’s magnetic sensor, which studied the magnetic fields within the mission’s landing zone. This shallow crater, known as “Homestead hollow”, is located in the region called Elysium Planitia – a flat-smooth plain just north of the equator. This region was selected because it has the right combination of flat topology, low elevation, and low debris to allow InSight to probe deep into the interior of Mars.
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Prior to this mission, the best estimates of Martian magnetic fields came from satellites in orbit and were averaged over distances of more than 150 km (93 mi). As Catherine Johnson, a professor of Earth, Ocean, and Atmospheric Sciences at the University of British Columbia and a senior scientist at the Planetary Science Institute (PSI), was the lead author on the study. As she said in a recent UBC News story:
“One of the big unknowns from previous satellite missions was what the magnetization looked like over small areas. By placing the first magnetic sensor at the surface, we have gained valuable new clues about the interior structure and upper atmosphere of Mars that will help us understand how it – and other planets like it – formed.”
“The ground-level data give us a much more sensitive picture of magnetization over smaller areas, and where it’s coming from. In addition to showing that the magnetic field at the landing site was ten times stronger than the satellites anticipated, the data implied it was coming from nearby sources.”
Measuring magnetic fields on Mars is key to understanding the nature and strength of the global magnetic field (aka. magnetosphere) that Mars had billions of years ago. The presence of this magnetosphere has been inferred from the presence of magnetized rocks on the planet’s surface, leading to localized and relatively weak magnetic fields.
According to data gathered by MAVEN and other missions, scientists predict that roughly 4.2 billion years ago, this magnetic field suddenly “switched off.” This resulted in solar wind slowly stripping the Martian atmosphere away over the next few hundred million years, which is what led to the surface becoming the dry and desiccated place it is today.
Because most rocks on the surface of Mars are too young to have been magnetized by this ancient field, the team thinks it must be coming from deeper underground. As Johnson explained:
“We think it’s coming from much older rocks that are buried anywhere from a couple hundred feet to ten kilometers below ground. We wouldn’t have been able to deduce this without the magnetic data and the geology and seismic information InSight has provided.”
By combining InSight data with magnetic readings obtained by Martian orbiters in the past, Johnson and her colleagues hope to be able to identify exactly which rocks are magnetized and how old they are. These efforts will be bolstered by future missions to study Martian rocks, such as NASA’s Mars 2020 rover, the ESA’s Rosalind Franklin rover, and China’s Huoxing-1 (HX-1) mission – all of which are scheduled to launch this summer.
InSight’s magnetometer also managed to gather data on phenomena that exist high in Mars’ upper atmosphere as well as the space environment surrounding the planet. Like Earth, Mars is exposed to solar wind, the stream of charged particles that emanate from the Sun and carry its magnetic field into interplanetary space – hence the name interplanetary magnetic field (IMF).
But since Mars lacks a magnetosphere, it is less protected from solar wind and weather events. This allows the lander to study the effects of both on the surface of the planet, which scientists have been unable to do until now. Said Johnson:
“Because all of our previous observations of Mars have been from the top of its atmosphere or even higher altitudes, we didn’t know whether disturbances in solar wind would propagate to the surface. That’s an important thing to understand for future astronaut missions to Mars.”
Another interesting find was the way the local magnetic field fluctuated between day and night, not to mention the short pulsations that occurred around midnight and lasted for just a few minutes. Johnson and her colleagues theorize that these are caused by interactions between solar radiation, the IMF, and particles in the upper atmosphere to produce electrical currents (and hence, magnetic fields).
These readings confirm that events taking place in and above Mars’ upper atmosphere can be detected at the surface. They also provide an indirect picture of the planet’s atmospheric properties, like how charged it becomes and what currents exist in the upper atmosphere. As for the mysterious pulses, Johnson and her team are not sure what causes them but think that they are also related to how solar wind interacts with Mars.
In the future, the InSight team hopes that their efforts to gather data on the surface magnetic field will coincide with the MAVEN orbiter passing overhead, which will allow them to compare data. As InSight’s principal investigator, Bruce Banerdt of NASA’s Jet Propulsion Laboratory, summarized:
The main function of the magnetic sensor was to weed out magnetic ‘noise,’ both from the environment and the lander itself, for our seismic experiments, so this is all bonus information that directly supports the overarching goals of the mission. The time-varying fields, for example, will be very useful for future studies of the deep conductivity structure of Mars, which is related to its internal temperature.”
This study is one of six that resulted from InSight’s first year of mission data, which can be accessed here. However, this is just the beginning for the InSight mission, which will wrap up its two-year primary mission towards the end of 2020. Of particular interest are the X-band radio measurements that will show how much Mars’ “wobbles” as it spins on its axis, which in turn will help reveal the true nature of the planet’s core (solid or liquid?).
Exciting times lie ahead for the many missions we have (or will be sending) to Mars! Be sure to check out this video of the InSight mission too, courtesy of NASA JPL:
Further Reading: UBC News, NASA, Nature Geoscience