A daytime high of 15 degrees Fahrenheit doesn’t sound too brutal for a winter day on Mars’ desolate surface. But it’s a different story at night. Temps regularly plunge to -138 degrees Fahrenheit just before sunrise.
While Mars’ newest visitor InSight is packed with sensors to monitor what’s going on below the red planet’s surface, it’s also measuring what’s happening above. The Auxiliary Payload Subsystem (APSS) is giving us a daily weather report from Elysium Planitia, a flat plain near Mars’ equator. Temperature, pressure, and wind speed measurements tell us what the average Martian winter day looks like.
Those chilly temps I mentioned above happened on February 11, and also included a peak wind gust of 28.2 mph.
Don Banfield, the mission lead for the APSS, explains how the instrument package helps InSight’s primary mission of detecting Marsquakes.
“For our mission, APSS will help us filter out noise in our data and know when we’re seeing a Marsquake and when we aren’t,” says Banfield. “But by operating continuously, we’ll also see a more detailed view of the weather than most surface missions, which usually collect data for just a few hours at a time.”
The Temperature and Wind for InSight (TWINS) instrument will tell the team back on Earth when strong winds are messing with potential seismic signals. This same instrument will also be used to study how much dust and sand is blown around by wind and dust storms. These dust storms pack whirling winds of nearly 60 miles per hour according to Banfield.
Pressure readings from APSS are also already picking up evidence of Mars storms raging in the northern hemisphere.
“Since the lander is close to the equator, I didn’t think we’d see any evidence of the storms that are 60-degrees north latitude, but we’re already seeing evidence of the high and low pressure-signal waves that create weather on Mars,” Banfield said. “We can see those waves all the way down near the equator, as the waves are big enough that they have a signature. That was a surprise.”
InSight’s primary mission is expected to last for two Earth years, or about 708 Sols (Mars day). And APSS will be gathering meteorological readings every second of every day. Not only will we see how temperatures, wind speed, and pressure readings change day to day – but InSight will show us the seasonal fluctuations too. Winter will soon give way to Spring with the Spring Equinox coming on March 23.