Don’t blame asteroids for the Late Heavy Bombardment! | astrobites
https://astrobites.org/2017/02/10/dont-blame-asteroids-for-the-late-heavy-bombardment/
Asteroids have a bad reputation. They may have wiped out the dinosaurs, and they have threatened the survival of humanity in many terrible movies.
Until today’s featured paper, asteroids were also blamed for the Late Heavy Bombardment (LHB, for short) – a period of time in the early solar system when the Moon,
the Earth, and the other rocky planets were hit with an unusually high amount of impactors from a variety of material in space. It lasted from the Sun’s formation
4.6 billion years (Gyr) ago until the impact that created the Orientale crater on the Moon 800 million years later (3.8 Gyr ago). Planetary scientists working on
the Apollo missions in the 1960s first hypothesized the LHB when astronauts brought back impact melt rocks from various craters that unexpectedly all dated back to
this time. The idea was later extended to include the rest of the inner solar system when planetary scientists found similar cratering histories on each of the rocky
planets. These LHB-era impacts are believed to have been caused by some combination of asteroids (from the asteroid belt), comets (from the Kuiper Belt and beyond),
and leftover material from the formation of the inner rocky planets. However, it is still not clear which of these three sources was the main culprit.
To address one part of this issue, Nesvorny et al. – the authors of today’s paper, ask: Were there enough impacting asteroids to account for all of the craters on
the Moon from the Late Heavy Bombardment?