There is a new meteorologist on Mars. Although NASA’s InSight spacecraft landed on the red planet in late 2018 to measure the planet’s geology — primarily by listening for earthquakes on Mars — it also brought along some advanced meteorological equipment.
The space agency has set up a website to share that information, which includes not only daily high and low temperatures, but also unprecedented hourly data on wind speed, direction and air pressure for InSight’s equatorial location in Elysium Planitia. “We thought it was something people could have fun with,” Don Banfield of Cornell University, who leads InSight’s weather science, told Ars.
Other spacecraft have brought similar temperature and wind sensors to Mars before, but none had such an accurate barometric pressure sensor. The new sensor is 10 times more sensitive than any previous instrument, allowing InSight to detect light movements in the Martian soil and extract details about the interior of the red planet from such movements. The weather is important for this.
Mars’ atmosphere can be very thin — typically ranging between 700 and 740 pascals at the surface, less than one percent of Earth’s surface pressure — but it can nonetheless cause slight slopes in the Martian surface. The barometric pressure sensor will therefore help scientists calibrate the lander’s seismometer so that any tilt due to higher or lower air pressure can be filtered out of the data. It’s actually quite amazing that even such a thin atmosphere can have a small effect on the surface of Mars and that InSight’s seismometer is sensitive enough to detect it.
A Mars mystery
Since InSight landed last November, Banfield and other scientists have eagerly studied data from the barometric pressure sensor and made a few discoveries. Some were expected, such as gravitational waves in the Martian atmosphere. The instrument measured these repetitive vibrations in the atmosphere most evenings. 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 found something mysterious in the pressure data on the surface of Mars. Twice a day on Mars, around 7 a.m. and 7 p.m., there are hiccups in what should otherwise be a gradual rise and fall in surface pressure. Initially, the scientists thought this effect must be caused by something on the lander, but eventually they were able to rule out a cause due to an anomaly of the instrument or a heating source on InSight.
This feature is repetitive and “somewhat strange,” Banfield said. It was not predicted in any of the global or regional weather models for Mars. Currently, the scientists think it must be some kind of atmospheric wave related to sunrise and sunset on Mars. Perhaps there are downdrafts moving away from a steep topography, related to the motion of the sun, that momentarily disrupt the atmospheric changes.
There have been fewer surprises in terms of temperatures and wind. The days on Mars are not too cold, with maximum temperatures of -10 to -15 degrees Celsius. The nights are bitterly cold where InSight is, dropping to about -95 degrees Celsius. Winds weren’t too surprising, though scientists have observed more dust devils than expected.
The interplay of dust and wind on Mars remains one of the open questions that scientists like Banfield want to better understand before humans visit the red planet. Dust plays a big role on Mars in how much energy the planet’s surface absorbs and how much it radiates back into space. Scientists also want to understand the minimal wind needed to lift dust from the surface, a necessary precursor to dust devils and dust storms. Banfield said he has built a sensor to make just such measurements and hopes to fly it on a future mission to Mars.