POLAR BLOG

Canadian Geographic - - DEPARTMENTS - BY JOHN BEN­NETT

Deep im­pact

NEW CRATER-MAP­PING TECH­NIQUES COULD CHANGE HOW AS­TRO­NAUTS PRE­PARE FOR THE MOON AND MARS

TTHE POLAR-DESERT en­vi­ron­ment of the High Arc­tic is ideal for study­ing an­cient land­forms, be­cause un­like other places, there is no soil and lit­tle veg­e­ta­tion to cover them up. In 2010, sci­en­tists made a ma­jor dis­cov­ery on the Prince Al­bert Penin­sula, on Vic­to­ria Is­land near the Nu­navut-north­west Ter­ri­to­ries border: a massive, pre­vi­ously un­known me­te­orite i mpact crater. Ge­ol­o­gist Gor­don Osin­ski of Western Univer­sity in Lon­don, Ont., has been ex­plor­ing this “Tun­nunik im­pact crater” since 2012, prob­ing its rocks for what they can re­veal about Earth and other plan­ets. When a large me­te­orite crashes to Earth, it cre­ates deep cracks in the ground, al­low­ing wa­ter to cir­cu­late through rocks in the crust that have been heated by the im­pact. Forced back to the sur­face by heat and pres­sure, the wa­ter emerges as hot springs. “Hot springs can be havens for mi­cro­bial life in an oth­er­wise harsh en­vi­ron­ment,” says Osin­ski. “They are where we think life on Earth may have orig­i­nated — and where life may have got go­ing on Mars too.” The first or­der of busi­ness, says Osin­ski, was ge­o­log­i­cal map­ping and sam­pling to an­swer es­sen­tial ques­tions about the crater’s size, when it formed and so on. “We use satel­lite data to steer us to po­ten­tially in­ter­est­ing sites, espe­cially ar­eas where we think there may once have been hot springs, called ‘fos­sil hot springs’ be­cause they were only ac­tive for about 100,000 years,” he says. The re­searchers then fly in, ex­plore and col­lect rock sam­ples for the lab. The cat­a­clysmic force of a large me­te­orite im­pact, such as the one that formed the Tun­nunik crater more than 100 mil­lion years ago, leaves be­hind tell­tale fea­tures called “shat­ter­cones,” which ge­ol­o­gists use to es­ti­mate a crater’s di­am­e­ter. Be­cause these are eas­ily vis­i­ble in the polar desert, Osin­ski’s team was able to as­sem­ble the most de­tailed shat­ter­cone map ever made. “We showed that Tun­nunik is 28 kilo­me­tres in di­am­e­ter,” he says, “and that’s a big crater. Also, we de­vel­oped a for­mula that we used to im­prove the di­am­e­ter es­ti­mates of quite a few other craters around the world.” This re­search, says Osin­ski, helps us un­der­stand the ge­o­log­i­cal his­to­ries of places such as the moon, Mars and Mer­cury, which are dom­i­nated by me­te­orite im­pact craters. And his work has a di­rect con­nec­tion with space ex­plo­ration: Cana­dian as­tro­naut Jeremy Hansen joined the crater ex­pe­di­tions to learn about ge­ol­ogy. “But,” says Osin­ski, “also to ex­pe­ri­ence an ex­pe­di­tion to a re­mote en­vi­ron­ment and learn how we ex­plore some­where we’ve never been be­fore. His time at the Tun­nunik im­pact crater will ben­e­fit fu­ture Cana­dian as­tro­nauts who go to the moon, Mars or some other ob­ject in the so­lar sys­tem.”

Ge­ol­o­gist Gor­don Osin­ski’s re­search team ex­plores the huge Tun­nunik im­pact crater on Vic­to­ria Is­land, N.W.T., col­lect­ing sam­ples to help map the an­cient land­form’s true ex­tent.

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