Mars density and escape velocity
From two simple numbers
- radius ~ 0.5 Earth
- mass ~ 0.1 MEarth
we can learn a lot. We can calculate its density relative to Earth and
the escape velocity from its surface. Recall that
This gives
- (escape velocity)2 ~ 0.2
(escape velocity)2Earth
The escape velocity is quite a lot smaller than Earth's, so we expect
that Mars may have trouble keeping a thick atmosphere.
For the density, we get
- density ~ 0.8 densityEarth
The density is similar to Earth's, so we expect the internal composition
to be similar, maybe with a smaller iron core.
The somewhat smaller density is in line with the hypothesis that the
original solar nebula was cooler farther out, so that the planets
further away from the sun formed out of less dense materials.
ASTR 121 Home
Davison E. Soper, Institute of Theoretical Science,
University of Oregon, Eugene OR 97403 USA
soper@bovine.uoregon.edu