"Long before it's in the papers"
August 28, 2009

RETURN TO THE WORLD SCIENCE HOME PAGE

Signs of recent Ice Age noted on Mars

Aug. 28, 2009
Courtesy Geo­phys­i­cal Re­search Let­ters
and World Science staff

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.

* * *

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, 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 argue. 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.