Thursday, September 24, 2009

Vast underground ice sheet found on Mars

NASA image shows water ice fading between October, 2008 and January, 2009

I've just finished listening to a NASA press conference announcing that nearly half of Mars has a layer of nearly pure ice just under its surface.

The NASA scientists estimate that this represents about one million cubic kilometers of ice, or about twice the amount of ice that covers Greenland here on Earth.

The Martian ice was exposed to view by meteorites that blasted out small craters--a few meters in diameter and from half a meter to two-and-a-half meters deep--and, much to the scientists' surprise, revealed a layer of 99 percent pure ice that they think ranges from 1 to 10 meters (33 feet) thick.

These underground ice sheets appear to extend from the Martian poles to about 45 degrees north and south--that is, halfway from each pole to the Martian equator.

Three different instruments in orbit around Mars on the Mars Reconnaissance Orbiter allowed the scientists to detect five newly formed craters, photograph bright, bluish-white material in or splashed out around them, material that quickly faded away during the Martian summer, and finally identify that material as nearly pure water ice by its spectrum.

"We found a beautiful water ice signature," said Selby Cull, from the Compact Reconnaisance Imaging Spectrometer for Mars team. "Crystal-clear-no-doubt-about-it water ice."

The ice is amazingly recent--around 10,000 years old--the scientists say. It dates from a period when Mars was wetter and had much more water vapor in its atmosphere than it does today.

According to the researchers, the discovery sheds light on the recent climate history of Mars, during which water vapor has shuttled out from and back to the polar regions as the Martian climate has warmed and cooled due to changes in the amount of sunlight the planet receives.

This plus earlier studies have led scientists to conclude that Mars had far more water in the distant past--several billion years ago--but has cooled and dried out over time. Some of the water is now locked up in minerals, some has been lost to space, and some remains in the form of ice.

In contrast, Earth has managed to keep most of its water.

Mars is now too cold, and its atmosphere is too thin, to allow liquid water to exist at the surface. However, these new findings suggest that water may still percolate underground, coalescing to form these newly discovered underground ice sheets.

Ironically, the Viking II spacecraft landed in the region where this ice was found in 1976, and scraped down into the soil, but not quite deep enough to find the ice.

"If Viking II had been able to dig down a few more inches, we could have made this discovery 30 years ago," said Shane Byrne, with the High Resolution Imaging Science Experiment.

The NASA scientists say they were not surprised to find ice under the surface of Mars, but were amazed to find that it was so pure. "We expected it to be a 50-50 mix of ice and dust," Byrne said. This has sent them back to their blackboards to try to explain what they found.

It may be decades or even centuries before humans set foot on Mars. The good news is that when we do get there, there will be plenty of water waiting for us just under Mars' cold and dusty surface.

Robert Adler
for the institute

Monday, September 14, 2009

An ill wind . . .

Third Roadsign Report from the institute

We sailed past yet another warning sign on our crash course towards irreversible climate change a few days ago.

As reported by the AP, two German-flagged cargo ships navigated the "northeast passage," powering their way from South Korea to Siberia (and on towards Rotterdam) via an arctic route that until now has always been blocked by ice.

Scientists cited in the AP story say that this is a clear indication of human-caused climate change, which has long been predicted to show up most dramatcally in Earth's arctic and antarctic regions.

It may be good news for shippers and other business interests who are eager to exploit the arctic, but it's not good news for the rest of us.

Earth's rapidly melting ice is thought to be one of the most likely triggers for irreversible climate change. Since ice reflects the sun's energy back into space, it helps to keep the planet cool. When ice is replaced with open ocean or terrain, solar energy is absorbed and retained. This sets up a feedback loop that melts more ice, which means more energy is absorbed--you get the idea.

At least, with President Obama rather than Bush in the White House, the U.S. is no longer actively blocking progress towards international agreements to fight climate change. However, the political will and skill to attack this enormous global problem still lag dangerously far behind the accelerating pace of global warming and climatic disruption.

Robert Adler
for the institute