From: andrew.gray@dunelm.org.uk   
      
   On 2005-02-25, Andrew Wright  wrote:   
   > Can anyone suggest why the (probable) frozen sea on Mars recently reported   
   > by ESA's Mars Express orbiter wasn't spotted earlier by Mars Global   
   > Surveyor? Also would it have appeared oddly flat in laser altimetry data?   
      
   Note that the Mars Express pictures were taken in January 2004; it's   
   quite possible no-one's got around to analysing any MGS images of the   
   area yet.   
      
   In addition, they resemble already-known formations thought to be lava   
   flows; it's quite possible that any photographs of the area with   
   sufficient resolution to pick out the plates were looked at, noted as   
   being another example of a known phenomenon, and thus not something that   
   leaped out as important. Here, the key seems to have been someone   
   noticing that they a) looked like pack-ice and b) were too large for   
   basalt rafts.   
      
   The area was definitely imaged by MGS; the abstract that's floating   
   around contains at least one photo from the MOC, and there's reference   
   to crater-counting using these images as well. It also notes the use of   
   MOLA data, so presumably either no-one noticed or it was just written   
   off as an anomalously flat area. Note that whilst it's very horizontal   
   it's not very flat - it still has craters and irregular surfaces - so   
   this wouldn't have been quite as much of a red flag as it may seem.   
      
   --   
   -Andrew Gray   
    andrew.gray@dunelm.org.uk   
      
   --- SoupGate-Win32 v1.05   
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