Mighty Dons Of Science News

Mars has app­par­ently un­der­gone a re­cent Ice Age, sci­en­tists say.

Re­search­ers drew the con­clu­sion based on the dis­tri­bu­tion of ice at and slightly be­low ground lev­el near the Red Plan­et’s po­lar re­gions.

Two hy­pothe­ses have been sug­gested to ex­plain this ice: that it fell there as pre­cipita­t­ion dur­ing re­cent ice ages, or that wa­ter va­por spread through the sur­face rocks, grav­el and soil.

To find out which al­ter­na­tive was cor­rect, Sam­u­el C. Schon of Brown Un­ivers­ity in Rho­de Is­land and col­leagues used da­ta from the High Res­o­lu­tion Im­ag­ing Sci­ence Ex­pe­ri­ment, or HiRISE, an im­ag­ing in­stru­ment aboard NASA’s Mars Re­con­nais­sance Or­biter space­craft.

The group ex­am­ined the struc­ture of ex­posed subsur­face Mar­tian ter­rain. The re­search­ers no­ticed that the ter­rain fea­tures lay­ered de­posits many me­ters (yards) thick that stretch over many hun­dreds of me­ters.

They sug­gest that cli­mate varia­t­ions are most likely the source of this stratifica­t­ion. The lay­ers probably formed as dust, ice, and snow were de­posited on the ground dur­ing re­cent ice ages, which oc­curred dur­ing pe­ri­ods when Mars’s ax­is of rota­t­ion was more tilted than usu­al, the sci­en­tists ar­gued.

Va­por dif­fu­sion would be un­likely to re­sult in the lay­ered struc­ture, they added. They note that the ob­serva­t­ions al­so sug­gest that sig­nif­i­cant subsur­face ice may re­main in the 30-50 de­grees mid-latitude re­gions.

The find­ings were pub­lished Aug. 6 on­line in the re­search jour­nal Geo­phys­i­cal Re­search Let­ters.