With the best atmospheric pressure sensor on Mars, scientists discover a mystery

There is a new meteorologist on Mars. Although NASA's InSight spacecraft landed on the red planet in late 2018 to measure the geology of the planet – mostly listening to the earthquakes on Mars – it also brought sophisticated weather equipment.

The Space Agency has set up a website to share this information, which includes not only daily highs and lows, but also unprecedented hourly data on wind speed, direction, and atmospheric pressure. InSight location near the Equator in Elysium Planitia. "We thought people might have fun with that," Don Banfield of Cornell University, who heads InSight's meteorological science, told Ars.

Other spacecraft have already brought comparable temperature and wind sensors to Mars, but none of them carried an air pressure sensor as accurate. The new sensor is 10 times more sensitive than any previous instrument, because InSight needs to detect slight movements on the Martian soil, which helps to infer details about the inside of the red planet. For that, time counts.

The Martian atmosphere can be very fine – it usually varies between 700 and 740 pascals on the surface, less than 1% of the pressure on the Earth's surface – but it can nevertheless induce slight inclinations at the Martian surface. . The atmospheric pressure sensor will therefore help scientists calibrate the landing gear seismometer so that any tilt due to higher or lower air pressure can be filtered out of the data. In fact, it is quite amazing that such a thin atmosphere can have a slight effect on the Martian surface and that the InSight seismometer is sensitive enough to detect it.

A Martian mystery

Since InSight landed last November, Banfield and other scientists have eagerly studied atmospheric pressure sensor data and made some discoveries. Some were expected, such as gravity waves in the Martian atmosphere. The instrument measured these repetitive oscillations in the atmosphere almost every night. Such gravitational waves are also observed in the Earth 's atmosphere, especially when a uniform air mass is disturbed by a mountain or island.

But scientists have also discovered a mystery in the pressure data on the surface of Mars. Twice a day in Martian times, around 7 am and 7 pm, there is a hiccup in what should otherwise be a smooth rise and fall of superficial pressure. At first the scientists thought that this had to be caused by something on the LG, but they were eventually able to eliminate a cause due to an anomaly of the instrument or a source of heating on InSight.

This feature is repetitive and "slightly strange," Banfield said. This was not expected in any of the global or regional climate models for Mars. Currently, scientists believe that this feature must be a kind of atmospheric wave related to the sunrise and sunset on Mars. Perhaps there are descending air flows of steep topography, related to the movement of the Sun, that briefly disrupt atmospheric changes.

In terms of temperatures and winds, there are fewer surprises. The Martian days are not too cold, with maximum temperatures between -10 and -15 degrees Celsius. In Inight, the nights are very cold and fall around -95 degrees Celsius. The winds were not surprising either, although the scientists observed more dust devils than expected.

The interaction of dust and wind on Mars remains one of the unresolved issues that scientists such as Banfield hope to better understand before humans go to the red planet. Dust plays a huge role on Mars in the amount of energy absorbed by the surface of the planet and in its amount of radiation in the space. Scientists also want to understand the minimum amount of wind needed to lift dust from the surface, a necessary precursor to devils and dust storms. Banfield said he had built a sensor to perform such measurements, and that he hoped to have it during a future Mars mission.