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Tycho Crater Oblique View Credit: NASA / Goddard / Arizona State University (Usage does not imply endorsement of site contents) |
A standard method for inferring the ages of planetary surfaces continues to be plagued by bad assumptions.To read the entire article, click on "Crater Count Dating: Self-Secondaries Reduce Age Estimates".
We’ve reported before about the problem of “secondary craters” in crater-count dating.* Planetary scientists have long used crater counts to estimate the age of a surface. In short, the more craters, the older the surface. That seemed reasonable until secondary cratering smudged the theory.
A single large impact (the primary) could launch up to a million pieces of ejecta (the secondaries) that fall back down, forming additional craters – all from that single event. Some large pieces could orbit for centuries before falling, and some could even travel between moons, messing up the ages of different bodies entirely. These realizations have tended to vastly reduce estimates of surface ages – not increase them. The assumption of ‘one impact = one crater’ is not necessarily true.
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