York U-led scientists issue Mars-Phoenix findings
TORONTO - Key findings of the Mars-Phoenix mission’s Canadian science team, led by York U, are published in Science.
During the five-month mission, which concluded in November of last year, the team’s laser instrument detected snow falling from Martian clouds a first in observations from the surface of the red planet.
“We found ice clouds and precipitation that were surprisingly Earthlike certainly more so than expected,” says York University professor Jim Whiteway, lead Canadian scientist.
In the Science article, Whiteway and 22 coauthors conclude that, had Phoenix operated further into winter, they would have seen evidence of precipitation accumulating into a seasonal buildup of water ice on the ground.
"Before Phoenix we did not know whether precipitation occurred on Mars. We knew that the polar ice cap advanced as far south as the Phoenix site in winter, but we didn't know how the water vapour moved from the atmosphere to ice on the ground. Now we know that it does snow, and that this is part of the hydrological cycle on Mars,” Whiteway says.
The mission obtained measurements from the surface in the Arctic region of Mars. The spacecraft landed before the summer solstice, and operated throughout the midsummer peak and decline in atmospheric water vapour, making it possible to observe the processes that contribute to the water cycle.
The team used a Canadian-designed light-detection-and-ranging (LIDAR) instrument that emitted pulses of laser light upward into the atmosphere and detected the backscatter from dust and clouds. The laser instrumentation was part of Phoenix’s meteorological station, which gathered crucial information about the climate on Mars via temperature, wind, and pressure sensors.
The LIDAR observed water-ice clouds in the atmosphere of Mars that were similar to cirrus clouds on Earth. Measurements of atmospheric dust indicated that the planetary boundary layer (PBL) on Mars was well-mixed up to heights of approximately four kilometers by summer daytime turbulence and convection. The water-ice clouds were detected at the top of the PBL and near the ground each night in late summer after the air temperature began decreasing.
Whiteway and his colleagues interpreted that water vapour mixed upward by daytime turbulence and convection forms ice crystal clouds at night, which then precipitate back toward the surface.
He says the publication of their findings cements a new chapter of knowledge about Mars.
“It was several years of difficult work with a high risk. It’s satisfying that we achieved something special.”
Phoenix’s meteorological component was a collaboration led by York University, in partnership with the University of Alberta, Dalhousie University, the University of Aarhus (Denmark), the Finnish Meteorological Institute, MDA Space Missions, and Optech Inc., with $37 million in funding from the Canadian Space Agency. The mission was a joint project of NASA’s Jet Propulsion Laboratories and the University of Arizona.