Comets are basically like dirty snowballs
-- made of dirt and ice," Al Hariri said.
Comets consist of a central nucleus a few kilometres across and are often likened to dirty snowballs
because they consist mostly of ice mixed with dust.
Astronomers call objects like this one comets, and they describe them as dirty snowballs
Near Earth Objects (NEOs) are either asteroids - large lumps of rock and iron left over from the formation of the solar system - or comets - dirty snowballs
of ice and dust which may measure two or three miles across.
The images quickly revealed that 67P violates the conventional wisdom of comets resembling smooth dirty snowballs
, said Rosetta team member Holger Sierks of the Max Planck Institute for Solar System Research in Gottingen, Germany.
Comets are dirty snowballs
in space, made from ice and dust that can be traced back to when the Solar System first formed from a soupy cloud of gas and molecules flung out by exploding stars.
But both of these dirty snowballs
have visited the inner solar system many times, and a significant fraction of their ice may have evaporated, leaving behind a dirtier, less reflective surface than Kuiper belt objects have, Stern says.
For years, astronomers have thought of comets as single, large bodies -- either massive, dirty snowballs
or, more recently, icy mudballs (SN: 3/14/92, p.