By University of Colorado Laboratory for Atmospheric and Space Physics
August 28, 2021
The High Resolution Imaging Science Experiment (HiRISE) camera aboard NASA’s Mars Reconnaissance Orbiter acquired this closeup image of a “fresh” (on a geological scale, though quite old on a human scale) impact crater in the Sirenum Fossae region of Mars on March 30, 2015. Credit: NASA/JPL/University of Arizona
Images from MAVEN’s imaging ultraviolet spectrograph before, during, and after the 2019 dust storm. Before the storm, ice clouds could be seen hovering above the soaring volcanoes in the Tharsis region of Mars. The ice clouds disappeared completely when the dust storm was in full swing and started to reappear after the dust storm ended. Credit: Chaffin et al., 2021
“Until now, Mars scientists didn’t realize how big of an impact regional dust storms have on the Martian atmosphere,” says Chaffin.
The study’s findings indicate that as the dust storm heats up the atmosphere, winds are generated that catapult water vapor to much higher altitudes than usual. At these highest altitudes, Mars’ atmosphere is sparse and water molecules are more vulnerable to ultraviolet radiation, which tears them into their lighter components of hydrogen and oxygen. The lightest element, hydrogen, is then easily lost to space. “All you have to do to lose water permanently is to lose one hydrogen NASA’s Mars Reconnaissance Orbiter measured the temperature, dust, and water-ice concentrations from the surface to about 62 miles, or 100 kilometers, above it. Within the same altitude range, the European Space Agency’s Trace Gas Orbiter measured the concentration of water vapor and ice, and the imaging ultraviolet spectrometer aboard NASA’s MAVEN spacecraft capped off the measurements by reporting the amount of hydrogen at the highest altitudes in Mars’ atmosphere, 620 miles (1,000 kilometers) above the planet’s surface.
Schematic of the cycle of hydrogen loss on Mars. Both the traditional loss mechanisms and the new concept of loss from dust storms are represented. Credit: Chaffin et al., 2021
It was the first time that so many missions had focused on a single event. “We’ve really caught the whole system in action,” says Chaffin.
“This paper helps us virtually go back in time and say, ‘OK, now we have another way to lose water that will help us relate this little water we have on Mars today with the humongous amount of water we had in the past,” says Geronimo Villanueva, a Martian water expert at
The coincident observations from four instruments, including MAVEN’s imaging ultraviolet spectrometer (IUVS), Trace Gas Orbiter’s Atmospheric Chemistry Suite and Nadir and Occulation for Mars Discovery (TGO), and the Mars Reconnaissance Orbiter’s infrared radiometer (MCS), show the Mars atmospheric response during a regional dust storm in 2019. The results indicate that regional dust storms play a major role in drying out the planet. Credit: Chaffin et al., 2021
The combined observations showed water vapor in the lower atmosphere before the dust storm began. As the dust storm increased, heating the atmosphere and generating winds, the instruments saw water vapor catapulted to higher altitudes. Trace Gas Orbiter found 10 times more water in the middle atmosphere after the dust storm started, which coincides precisely with data from the infrared radiometer on the Mars Reconnaissance Orbiter. The MAVEN observations 650 miles above the surface also concurred, showing a 50% increase of hydrogen during the storm.
Collectively, the data from the three spacecraft paint a clear picture of how a regional dust storm can help Martian water escape. “The instruments should all tell the same story, and they do,” says Villanueva.
“It was an honor to lead this fantastic international team and help bring this result to light. Studies like this one demonstrate the power of cross-mission and international collaboration to drive Mars science forward,” says Chaffin.
For more on this research, see International Trio of Mars Orbiters Shows Small Dust Storms Help Dry Out the Red Planet.
Reference: “Martian water loss to space enhanced by regional dust storms” by M. S. Chaffin, D. M. Kass, S. Aoki, A. A. Fedorova, J. Deighan, K. Connour, N. G. Heavens, A. Kleinböhl, S. K. Jain, J.-Y. Chaufray, M. Mayyasi, J. T. Clarke, A. I. F. Stewart, J. S. Evans, M. H. Stevens, W. E. McClintock, M. M. J. Crismani, G. M. Holsclaw, F. Lefevre, D. Y. Lo, F. Montmessin, N. M. Schneider, B. Jakosky, G. Villanueva, G. Liuzzi, F. Daerden, I. R. Thomas, J.-J. Lopez-Moreno, M. R. Patel, G. Bellucci, B. Ristic, J. T. Erwin, A. C. Vandaele, A. Trokhimovskiy and O. I. Korablev, 16 August 2021, Nature Astronomy.
This research was funded in part by the MAVEN mission. MAVEN’s principal investigator is based at LASP, and NASA Goddard manages the MAVEN project.