York-led scientists issue Phoenix-Mars findings

Key findings of the Phoenix-Mars mission’s Canadian science team, led by York University, have been published in the journal Science. The report, published on Friday, summarizes the scientific findings of the mission, which was conducted last summer on the planet Mars.

During the five-month mission, which concluded in November 2008, 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 Earth-like – certainly more so than expected," says Professor Jim Whiteway, the lead Canadian scientist and Canada Research Chair in Space Engineering and Atmospheric Science in York’s Faculty of Science & Engijneering.

Left: Professor Jim Whiteway. Photo courtesy of the Canadian Space Agency 

In the Science article, "Mars Water-Ice Clouds and Precipitation," Whiteway and 22 co-authors 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," explains Whiteway.

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 kilometres – 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," says Whiteway. "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.

For more on the Phoenix-Mars mission, see YFile, Nov. 12, 2008, Aug. 15, 2008 and May 30, 2008.