Re: What is the temperature of an asteroid in the Astroid belt?

Erik,

  The near-Earth asteroid known as "433 Eros" appears to have a daytime 
temperature of about 100 degrees C (212 deg. F) and a nighttime 
temperature about -150 deg. C (-238 deg. F).  The NEAR (Near Earth 
Asteroid Rendevous) mission will visit this asteroid to make better 
measurements.

  The dust in out Solar System in the vicinity of the Asteroid Belt show 
temperatures as warm as -75 deg. C (-100 deg. F).  This temperature was 
measured by the Infrared Astronomical Satellite (IRAS).

  The average temperature in space has been measured to be about -270 deg. 
C (-454 deg. F).

  The observed colors of the most common types of asteroids are usually 
very dark.  This means that they will be warmer than the space around them 
because they will absorb the light that reaches them.

  We need to send spacecraft (the NEAR mission for example) to chosen 
asteroids and to the asteriod belt to measure the temperatures.  Until we 
do this we know only that the temperatures will be warmer than -270 deg. C 
and colder than about 100 deg. C.  The actual temperature depends on how 
much light (energy) is being absorbed by the asteroid.  As we move further 
from the sun the asteroids will be colder.

John Haberman, Space Scientist
NASA/Goddard Space Flight Center