Earth’s new­est is­land has clues to Mars’ past

Ge­o­log­i­cal sim­i­lar­i­ties could help shed light on an­cient Mar­tian his­tory.

Cosmos - - Digest -

The planet’s youngest is­land was not ex­pected to sur­vive more than a few months. Its sur­vival makes it a ge­o­log­i­cal trea­sure trove that may hold clues to ques­tions about an­cient Mars.

Hunga Tonga Hunga Ha’apai, in the ar­chi­pel­ago ßof Tonga, rose out of the South Pa­cific ocean in a month-long vol­canic erup­tion from De­cem­ber 2014 to Jan­uary 2015 – so fast you could watch it grow.

A cone of loosely con­sol­i­dated vol­canic ash formed the is­land, which sci­en­tists ex­pected the South Pa­cific surf to pound back in months. But it per­sists, stand­ing 120 me­tres tall at its high­est point and mea­sur­ing about two kilo­me­tres across, sci­en­tists re­ported at a meeting of the Amer­i­can Geo­phys­i­cal Union in New Or­leans in De­cem­ber.

They now think Hunga Tonga Hunga Ha’apai could last any­where be­tween six and 30 years. One rea­son for this longevity is the eroded ma­te­rial pil­ing up in the shal­low wa­ters that has con­nected it to two neigh­bour­ing is­lands and formed a more stable bar­rier.

“That’s al­low­ing the sys­tem to par­tially sur­vive,” says Jim Gavin, of NASA’S God­dard Space Flight Cen­tre.

The chance to study the is­land’s evo­lu­tion not only helps bet­ter un­der­stand the his­tory of Earth but also of Mars, which has thou­sands of ge­o­log­i­cal fea­tures with sim­i­lar size and shape.

Many sci­en­tists think those fea­tures might be due to vol­canic erup­tions be­neath shal­low seas about one to two bil­lion years ago. What were once Mar­tian is­lands were left as low iso­lated peaks when oceans dried up.

Study­ing Hunga Tonga Hunga Ha’apai might help de­ter­mine the depth of the wa­ter in which these Mar­tian is­lands sat and how long that wa­ter per­sisted. Not that the par­al­lel is per­fect; what­ever oceans ex­isted on Mars were nowhere near as big as the Pa­cific Ocean. So the pro­cesses af­fect­ing the Mar­tian is­lands would be much slower than those af­fect­ing the new Ton­gan is­land.

None­the­less, Gavin says, Hunga Tonga Hunga Ha’apai “will give us win­dows onto the times on Mars when we think there were stand­ing bodies of wa­ter” – one of the “holy grails” of Mar­tian an­cient his­tory.

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