|
If we can see impact craters on the Moon "next door", why
don't we see them on Earth?
When
you look up at the moon, numerous huge circular features are visible as
lava-filled impact basins, smaller impact craters are readily visible
in binoculars and telescopes, and we can even find micrometeorite impacts
in space equipment left on the surface of the moon for a long time. Clearly,
the moon has been bombarded at nearly every scale size we can see, and
it is still receiving at least a little space debris today. But why-with
Earth so nearby-do we only around 150 very worn down craters on Earth?
The Earth has both an atmosphere and oceans, and together they are capable
of filling in and wearing away evidence of impacts in mere millions of
years. This is just a blink in time for the moon, which displays billions
of years of accumulated impact scars. The cratering rate of the two bodies
is actually very similar, but the more dynamic Earth has a more efficient
system to erase the evidence.
This
week's question is provided by Susan Sakimoto, a research scientist employed
through the Goddard Earth Science and Technology (GEST) Center at UMBC.
She has been a member of the Geodynamics Branch for about 5 years, is
an expert on Earth and planetary volcanism, and has been extensively involved
in both the analysis of Mars Orbiter Laser Altimeter (MOLA) data and field
studies of small volcanic constructs in the Eastern Snake River region
(likely analogs for small volcanoes on Mars). Susan teaches a course for
secondary school teachers at Johns Hopkins ("Teaching the Solar System")
and has been greatly involved in mentoring activities for students ranging
from high school to graduate school.
|