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one of the most challenging aspects of

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this mission happens before we even land

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and it's picking the right landing site

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for the mission we want to study the

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habitability of Mars we want to really

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figure out if it was ever capable of

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supporting life and the way we do that

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is to really follow the evidence of

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water on Mars one of the most

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interesting things about Mars is that

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it's changed over time what we see on

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Mars today is very different from what

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occurred in the distant past and water

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is the real interesting thing that we're

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looking for the history of water how

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it's changed over time one of the

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biggest challenges to studying

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habitability on Mars which is the goal

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of the Curiosity rover mission is to try

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to follow that signature of water where

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is where was the water how long was it

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there and where do we go to look for

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evidence of it if we were somewhere like

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this where there's a pretty obvious

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geologic record of water flowing

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carrying material down that would be a

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home run but the real challenge is

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finding that one spot on Mars to send

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we have four wonderful landing sites all

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very different in character and the real

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challenge for us as scientists is to

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come to a consensus on which one of

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those sites offers the best chance

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fulfilling the goals of the mission

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there's a place on Mars called Mars

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Valles which has the brightest mineral

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signature of clay minerals on mars and

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these clay minerals are known to form in

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the presence of water and neutral pH

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water not acidic not too basic just the

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kind of water that you thought it would

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be friendly to life then you have

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terrestrial geologists who say that the

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rock record should be the thing that we

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follow the landforms that look like they

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were carved by rivers or floods so you

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have sites like Holden crater which is a

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big impact crater many miles across with

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a river coming into it perhaps forming a

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lake multiple times and flooding the

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crater leaving a geologic record that we

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can study with curiosity just upstream a

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little bit from Holden crater there's a

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place called Evers wal crater that same

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river system in Everest walls has left

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evidence of a delta just like the

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Mississippi River Delta these things

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form when muddy silty water deposits

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it's silt smudge into a formation into a

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standing body of water like a lake so

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you have people that study Delta's on

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earth you think that's the place

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curiosity should go the final site is

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the best place on Mars if you want to

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just study layered materials so why why

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do we like layered materials because

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just like this outcrop behind me they

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give a record of time of how things

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change over time by studying different

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layers you can rebuild the geologic

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so there's a place called Gale Crater

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which has a 3-mile stack of layered

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rocks now we don't exactly know how much

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how those layers formed and the

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mineralogical evidence isn't as strong

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as other sites but people who just think

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layers are the thing to study really

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love Gale so you have these four

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different sites and these four different

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groups and very passionate arguments

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back and forth to try to really narrow