When he was around the age of 5, Isaac Smith experienced a life-changing moment. His mother took him to see Halley’s Comet pass by overhead. Away from the city lights of Houston, surrounded by woods and clear skies, Smith witnessed the smoldering passage of the comet as it painted a streak across the night sky. It was one of his first memories.
“Since then, I’ve always been fascinated with space,” Smith told R&D Magazine. “That would have been the start of it all.”
Now a postdoctoral researcher with the Southwest Research Institute, Smith is part of a team that uses the Shallow Radar sounder (SHARAD) instrument aboard the Mars Reconnaissance Orbiter to study ice caps on the Red Planet.
Recently, Smith and colleagues discovered evidence of ice ages on Mars, confirming hitherto theoretical models regarding the movement of ice on the planet from the polar regions. They reported their findings in Science.
“In 2003, there was an article that suggested up to a 1-meter equivalent of a global (ice) layer … and what I mean by that is if you took (ice) away from the poles and spread it over the whole planet, it would be a meter thick. That’s a lot if ice,” said Smith. Since the last ice age, which ended roughly 370,000 years ago, “we found that 60 cm had moved between the poles and the mid-latitudes and that’s really good agreement with (a) one meter” global spread.
Additionally, he said, a research group in 2007 predicted a 300-meter accumulation of thickness in ice on the polar caps. Smith and colleagues, based on their radar images, saw an accumulation around 320 meters thick. Most of the accumulation occurred on the north pole.
“The evidence is really compelling when you take into account the predictions,” he said.
Currently, Mars’ ice is in a state of retreat, something the researchers discovered by glimpsing thousands of radar images, which were taken every two hours by the SHARAD.
Whether the ice is in a state of retreat or spread is determined by a myriad of factors. Over millions and millions of years, Mars’ tilt changes substantially, sometimes up to 60 degrees. Additionally, the orbit is heavily affected by a gravitational tug from Jupiter, which pulls it into an oval-shaped orbit. This means sometimes the north pole faces the sun, and other times the south pole faces the sun.
When the poles get warm, Smith said, ice leaves the regions and travels to the low- and mid-latitude regions where it can remain stable.
“We can actually know fairly decently … the timing of these things,” Smith said, noting that based on predictive models Mars’ next ice age will occur in about 150,000 years.
Understanding these shifts has implications for eventual attempts to send humans to Mars. After all, humans need to drink water, they need to shower, and they need to make rocket fuel.
“So they’re going to land where we can find the water,” said Smith.
Mars is in the midst of its closest approach to Earth. On May 30, the planet will be less than 47 million miles away.
“Because of that, it’s really big in telescopes and it’s really bright,” added Smith. “If you just look up around midnight, it’ll be straight above your head. It’ll be the bright red gem in the sky. It doesn’t twinkle, it’s just brilliant red.”
Last weekend, Smith viewed the planet from the Griffith Observatory in Los Angeles. “You can see the colors,” he said. “It’s light red, and dark red, and there’s clouds, and there’s ice caps.”
But Mars may have not always been the brilliant red it is today. About half a million years ago, according to Smith, the ice may have been so spread out that it could have tinted the planet white or pink.
That’s “a cool visual I like to think about,” he concluded.