Monitoring Martian Weather, Part 1: On the Ground

NASA’s InSight lander has been making a splash in the news thanks to its capable weather station—but it’s not the first robotic meteorologist we’ve had on Mars.

Last week, NASA unveiled the first weather data from its InSight lander, which arrived on Mars in late November of last year. With a primary goal of collecting seismic and heat flow data to help us learn about the interior structure of the Red Planet, InSight also requires extremely sensitive information about martian weather. This is because it needs to be able to distinguish possible “marsquakes” and underground temperature swings from other disturbances, such as gusts of wind. The Auxiliary Payload Subsystem (APSS) measures air temperature, pressure, and wind through a suite of sensors across the lander. You can view InSight’s daily weather report here.

A recent weather report from NASA’s InSight lander. Image credit: NASA/JPL-Caltech

InSight isn’t the first mission on the surface of Mars to collect data about the weather. NASA’s Viking 1 and 2 landers in the mid-1970s each carried a Viking Meteorology experiment consisting of air and ground temperature sensors, a pressure sensor, and a wind speed and direction sensor. Viking 1 initially returned daily weather reports, decreasing in frequency to weekly later in the mission, until contact with the lander was lost in February 1983.

The weather instrument package aboard the Viking 1 lander, 1976. Mounted atop the extended boom, the meteorology sensors stood about four feet above the martian surface and measured atmospheric pressure, temperature, wind velocity and wind direction. Image credit: NASA/JPL

The Viking landers also had an additional unintended weather instrument onboard. Meant to hunt for the existence of marsquakes, the seismometers suffered a critical design flaw: They were mounted to the deck of each lander. This resulted in noise in the data due to wind moving the legs of the lander. While this rendered the instruments nearly useless for their intended purpose, it did give valuable information about the winds of Mars — including possibly detecting dust devils zipping past the lander.

The seismometers on Viking 1 (left) and 2 (right). Image credit: NASA/JPL

In 1997, Mars Pathfinder was the next successful visitor to the Red Planet’s surface. Armed with its Atmospheric Structure Investigation/Meteorology (ASI/MET) Experiment, Pathfinder was able to measure temperature and wind speed at a few different heights compared to the single-height measurements of the Viking landers. This ability led Pathfinder to discover huge temperature variations—a difference of over 40°C in some cases—within a mere 5-foot range above the ground. Pathfinder was also the first mission to visibly spot dust devils from the surface of Mars. These small whirlwinds had been spotted from orbit by Viking and Mars Global Surveyor, but never directly seen in images from the surface. Their passage was merely inferred from other meteorological data collected by the landers, such as rapid changes in air pressure.

Enhanced colour view of a dust devil imaged by Pathfinder in 1997. Image credit: NASA/JPL/Mark Lemmon

Example of a weather report from Pathfinder. Image credit: NASA/JPL

It would be a decade before another surface mission arrived at Mars with a dedicated weather monitoring system. In 2007, NASA’s Phoenix lander set down on the northern plains to give us our first glimpse of Mars’ version of the icy Arctic. A Canadian-built meteorological station onboard carried temperature and pressure sensors and a light detection and ranging (LIDAR) system. This LiDAR was responsible for perhaps the most fitting discovery in the Solar System: Canadians discovered snow on Mars. Like virga on Earth however, this snow only occurs high up in the martian atmosphere and never reaches the ground. (Phoenix did observe early morning frost depositing on the ground, as well as on itself.)

Early morning frost accumulating on the Phoenix lander’s wind telltale in August 2008. Image credit:NASA/JPL-Caltech/University Arizona/Texas A&M University/University of Aarhus/University of Copenhagen

NASA’s Curiosity rover landed on Mars in 2012 with its Spanish-built Rover Environmental Monitoring Station (REMS). Through a suite of sensors on the rover deck, inside the electronics box, and small booms on the rover mast, REMS takes measurements of air and ground temperature, humidity, wind speed and direction, and ultraviolet radiation levels at the surface. Weather reports from REMS are released online a few times per month.

A recent weather report from the Curiosity rover’s REMS instrument package. Image credit: NASA/JPL-Caltech/MSSS/CAB/CSIC-INTA

NASA’s upcoming (as-of-yet unnamed) Mars 2020 rover will be equipped with a weather instrumentation suite similar to Curiosity’s, but with an added feature: The ability to measure and characterize dust in the atmosphere. Thanks to this, the Mars Environmental Dynamics Analyzer (MEDA), again provided by Spain, will help us better understand the martian dust cycle and the impact it has on weather.

In addition to all of these ground-based weather measurements, we’ve been spying on Mars’ weather from orbit—and afar—for centuries. Stay tuned for part 2 next week, delving into this data.