document: The Mars Connection Jeffrey Marlow , a graduate student at the California Institute of Technology , writes from New Mexico , where he is measuring sand particle sizes , layer thicknesses and angles to address questions about volcanoes and rock patterns on Mars . Saturday , March 26 The base surge deposits of Kilbourne Hole and Hunt 's Hole are part of a much larger story , a story that starts on the desolate plains of Mars in 2003 . As the Mars Exploration Rover -LRB- M.E.R. -RRB- Opportunity started surveying its outpost , it found several tantalizing features that pointed to a water-rich history . There was the crossbedding , the salt minerals that seemed to precipitate from an evaporating lake , and the famed '' `` blueberries '' '' -- accretionary spherules formed by the movement of water through local rock . But science is all about exhausting every opportunity to prove a theory wrong , and only then accepting it with caveats of probability and likelihood . Many of the devil 's advocates pointed to base surge deposits -- citing the crossbedding and lapilli spheres -- as viable alternatives , suggesting that the sedimentary environment on Mars was volcanic . Lauren Edgar , the doctoral student leading our expedition , also works on the M.E.R. missions , and she recalls : '' `` There was a lot of debate about the origin of the sediment -- was it deposited in damp to wet , subaqueous conditions , or was it part of a volcanic base surge deposit like the ones we 're observing at Kilbourne Hole and Hunt 's Hole ? '' '' Jeffrey Marlow Volcanic Rocks Just North of the Border Into a Lunar Training Ground Distinguishing between these possibilities has tested the rover 's scientific arsenal . '' `` On Earth , we usually have a lot more context , so it 's easier to make these distinctions , '' '' says Lauren . '' `` But on Mars , when you 're dealing with just a small snapshot of the deposit , it can be a lot harder . '' '' Despite the cosmetic similarities , the rover team 's consensus at the moment is that water was required to produce some of the sedimentary features that Opportunity has encountered . Nonetheless , it 's pretty likely that base surge deposits -- volcanic or impact-induced -- are abundant on Mars . John Grotzinger is advising Lauren 's work with the maar deposits and is the project scientist for the coming Mars Science Laboratory mission . '' `` The early history of Mars was characterized by enormous numbers of bolide impacts that struck the surface of Mars , sending plumes of debris high into the atmosphere '' '' he notes . '' `` As these plumes settled back down to the surface they created base surge deposits . '' '' Thus , establishing a set of criteria to help distinguish base surge sediments from water-based deposits is a critical step in reconstructing ancient Martian environments . As John puts it , '' `` It 's important that we be able to distinguish the two , since only subaqueous conditions have strong potential as habitable environments . '' '' One potentially useful marker we 've noticed here in New Mexico is the distribution of lapilli -- the ashy hailstones that fall out of a cloud of volcanic debris . While the blueberry concretions on Mars are distributed throughout the rock , here the spherules occur only in certain layers , reflecting the periodic , discrete nature of the volcanic hailstorms . Initial results also suggest that the sudden changes in grain size between rock layers and the specific angles of the sedimentary signatures may be additional criteria to help diagnose a base surge deposit . As the sun sets on our final evening and periodic dust devils swirl on the desert plain to the south , I look into the crater and find it easy to imagine myself on Mars . Cue the red filter , cut the vegetation , dial the thermostat back a bit , and you would be hard pressed to tell the two worlds apart . Of course , the differences between the Red and Blue Planets are significant , and with continued sedimentological studies on Mars -- and Earth-based analogues like Hunt 's Hole and Kilbourne Hole -- we should be able to paint a more complete picture of what Mars was like in the past . As with most fieldwork , much of the real work comes back in the lab as samples are processed and photographs are analyzed , but it 's clear that base surge deposits produce unique depositional features that will hopefully be resolvable with current and future Mars missions . With samples stowed and a healthy sheen of desert dust covering us , we head back to El Paso , leaving the craters to the coyotes .
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