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Credit & Copyright: NASA,  
Johns Hopkins Univ. APL,  
Arizona State U., CIW  
  
  
Explanation:
The sprawling Caloris basin  
on Mercury  
is one of the solar system's largest  
impact basins,  
created during the early history of the solar system by the impact of  
a large asteroid-sized body.  
  
The multi-featured,  
fractured basin spans about 1,500 kilometers in this  
enhanced  
color mosaic based on image data from the Mercury-orbiting  
MESSENGER spacecraft.  
  
Mercury's youngest large impact basin,  
Caloris was subsequently filled  
in by lavas that appear orange in the mosaic.  
  
Craters made after the flooding  
have excavated material from beneath the surface lavas.  
  
Seen as contrasting blue hues, they likely offer a glimpse of  
the original basin floor material.  
  
Analysis of these craters suggests the thickness  
of the covering volcanic lava to be 2.5-3.5 kilometers.  
  
Orange splotches around the basin's perimeter are thought to be  
volcanic vents.  
  
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NASA Web Site Statements, Warnings, and Disclaimers
NASA Official: Jay Norris. Specific rights apply.
A service of: LHEA at NASA / GSFC
& Michigan Tech. U.
Based on Astronomy Picture
Of the Day
  