THEY are both breathtaking, in quite different ways: the thin air 4200 metres up, and the majestically rugged, alien landscape at my feet.
I am on the summit of Mauna Kea, the highest point in Hawaii. The red-brown basalt and barren surface of the dormant volcano conjure up images of Mars.
It was in the Pu鈥檜 Wekiu crater, in 1969, that the geophysicist Alfred Woodcock dug beneath the rocky exterior and discovered a hidden ice world. But when Norbert Sch枚rghofer, an astronomer at the University of Hawaii at Manoa, stumbled across Woodcock鈥檚 papers decades later, he was baffled. How could ice persist in an area where the average temperature is 4 掳C?
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To try to solve this puzzle, Sch枚rghofer has enlisted the help of geophysicist and permafrost expert Matthias Leopold at the University of Western Australia in Perth. The goal of the expedition I have come on is to find out whether the subterranean ice patch still exists.
Sch枚rghofer buried some temperature sensors here in 2013, and when we get to the third of these, a metre deep in the centre of Woodcock鈥檚 old surveying area, he lets out a whoop of excitement. The temperature here is freezing.
鈥淪adly, time is running out for a precious window on how and why buried ice forms on the Red Planet鈥�
To investigate further, Leopold spaces out 20 steel electrodes, each the size of a tent peg, across the survey area. These generate an electric field that can find frozen ground up to 50 metres deep by measuring resistivity. Unlike drilling, it preserves the landscape that local people hold sacred.
The readings show that the ice is still there, but its horizontal extent has shrunk from 600 to 200 square metres, and its depth halved to just 5 metres. Global warming may have played a part in this, but it鈥檚 hard to tell without long-term data.
The team will now combine geological and meteorological data to come up with a theory of why the buried ice persists. The most plausible explanation is that it forms at night, when temperatures drop below zero and icy air can swirl down the steep crater and seep into the porous, rocky ground. Any ice formed would normally melt in the daytime heat, but this patch sits in a dark crater.
Mauna Kea is one of the best models on Earth for studying ice within the tropics of Mars, says Sch枚rghofer. Most of the Red Planet鈥檚 ice is at the poles, but photos have identified signs of buried ice towards the equator. Just like with Pu鈥檜 Wekiu, these spots lie in shadow inside the steep craters that punctuate the planet鈥檚 surface.
Not much is known about ice away from Mars鈥檚 poles, so Mauna Kea鈥檚 ice is a precious window on how and why it forms. But sadly, its time is running out. With climate change, Sch枚rghofer believes the Mauna Kea ice will disappear over the next 50 years.
As we drive back down, the only visible hint of where we have been is the volcanic ash on our faces. But hopefully, this won鈥檛 be my last trip to Mars.
This article appeared in print under the headline 鈥淭he volcano that hides ice like Mars鈥�
