WASHINGTON – Icy snow falls from high in the Martian atmosphere and may even reach the planet’s surface, scientists working with NASA’s Phoenix Mars lander reported Monday.
Laser instruments aboard the lander detected the snow in clouds about 2 1/2 miles above the surface and followed the precipitation as it fell more than a mile toward the ground. But because of limitations with technology, it was unclear whether any of the powdery stuff made it all the way to the Martian surface.
“Nothing like this view has ever been seen on Mars,” said Jim Whiteway of York University in Toronto, lead scientist for the Canadian-supplied Meteorological Station on Phoenix. “We’ll be looking for signs that the snow may even reach the ground.”
In addition to finding snow, the Phoenix team reported that they had discovered material in the Martian soil that had once been dissolved in water – clays and calcium carbonate (limestone) that could only have formed in the presence of liquid water. While the lander’s instruments had earlier found water ice below Mars’ polar surface and had photographed surface fog and clouds, it has found nothing like liquid water on the surface.
The presence of nutrients and other material that once dissolved in water, however, plus the continuing presence of water as snow, vapor and ice, is leading researchers to the conclusion that Mars’ polar regions might have supported life in the past – when the region was much warmer. Because Mars wobbles on its axis far more than Earth – in some very long-term cycles the poles actually face the sun – the northern region where Phoenix landed has, in the past, been warm.
“Is this a habitable zone on Mars? I think we are approaching this hypothesis,” said Peter Smith of the University of Arizona, the lander’s principal investigator.
In addition, Michael Hecht of NASA’s Jet Propulsion Laboratory said that further analysis of the Martian dust by the lander’s on-board laboratory has determined that it is as alkaline as ocean water, with a pH of 8.3. He said this finding also suggests that life could have existed on Mars.
The snow, along with frost and fog, began to appear about a month ago, Whiteway said, as temperatures cooled on Mars. “This is now occurring every night,” he said.
In an interview following the teleconference, Whiteway likened the snow to “diamond dust” that falls in the Arctic and Antarctica.
“What this is telling us is that water does rise from the ground to the atmosphere and then precipitates down,” he said. “So there is a hydrological cycle on Mars, and now other experts will study the data and try to determine what it all means.”
Although the Phoenix instruments could not determine whether the snow hit the ground, Whiteway said there are some indications that it does. Images of the thin but distinct Martian clouds can be seen at the NASA Web site, www.nasa.gov/phoenix.
Scientists have previously theorized that snow falls on Mars, but they had never before seen it in real time. Future research on the data collected by Phoenix will try to determine where the snow came from – whether it all originated in the ice-covered polar regions or evaporated from the broader Martian surface, or even from the large collections of ice below the surface.
The Phoenix team was surprised early this summer by the presence of the chemical perchlorate in the Martian soil. Used in many industrial capacities and in rocketry, the potentially toxic chemical is also found in the driest deserts on Earth. Smith said its presence on Mars suggests again that there was once liquid ground water and raises the possibility that Martian life has existed in the planet’s seemingly hostile environment.