Goddard Space Flight Center
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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.