Completely destroying the Moon to avoid the debris reassembling into a satellite would require an amount of energy larger than the Moon gravitational binding energy, estimated to be 1.2 × 1029J.[2][3][4] This equals a bit less than 600 billion 50-megaton nuclear bombs, such as the Tsar Bomba,[5][4][2][6] roughly equivalent to the full energy output by the Sun in six minutes.[4] For comparison, the impact that created the South Pole-Aitken basin, the largest lunar impact structure, had an energy of roughly 4 × 1026 J, 300 times smaller.[7] Bringing the Moon's orbit within the Roche limit of Earth (within about 18,000 km (11,000 mi)) would also destroy it.[3]
Without the Moon, tides would still happen—the Sun's gravity also causes tides—but they would be substantially reduced,[8] a quarter of the size of the current spring tide.[9] The sudden disappearance of the Moon however could release water pressure and create large potentially catastrophic waves around the oceans.[8] The reduction of tides could have profound negative consequences on coastal ecosystems.[10] Tides also help to drive ocean currents; without the Moon, weather extremes and major weather events would be more common.[10]
In 1993 numerical simulations suggested that the Moon is necessary to keep the Earth's axial tilt stable. Without the Moon the axial tilt of Earth could therefore oscillate chaotically from 0° to 45° on the scale of tens of thousands of years, possibly reaching 85° on timescales of several million years,[11] with severe climatic consequences.[9][4][6] More recent studies however suggested that, even without the Moon, Earth's axial tilt could be relatively stable on the scale of hundreds of millions of years.[12] Without the Moon, neither solar nor lunar eclipses would exist.[9]
Violent destruction of the Moon would likely bring substantial debris to impact Earth. Such debris would be slower, and thus each debris fragment have only about 1% of the kinetic energy with respect to an asteroid of the same size, therefore their impact would be less destructive.[9] However, their sheer quantity could lead nonetheless to substantial atmospheric heating, possibly leading to extinction of life on Earth.[4][6] The mathematician and Usenet personalityAlexander Abian proposed that the destruction of the Moon would stabilize seasons and eliminate natural disasters from Earth.[13] Apart from being practically unfeasible,[5] Abian's claims have no scientific basis— destroying the moon would actually cause natural disasters.[8]
Natural satellites can and do get destroyed. The rings of Saturn possibly originated from the destruction of a former moon, called Chrysalis.[14] The capture of TritonbyNeptune possibly destroyed some of the previous moons of Neptune, by crashing them on Neptune or Triton itself.[15][16] In turn, tidal interactions also cause Triton's orbit, which is already closer to Neptune than the Moon is to Earth, to gradually decay further; predictions are that 3.6 billion years from now, Triton will pass within Neptune's Roche limit and be destroyed.[17] The Mars moon Phobos is expected to meet a similar fate.[18] Phobos gets closer to Mars by about 2 cm per year, and it is predicted that within 30 to 50 million years it will either collide with the planet or break up into a planetary ring.[19] Outside the Solar System, exomoons might collide with planets, removing life from them. [20]
^Hansen, Bradley M S. (2023). "Consequences of dynamically unstable moons in extrasolar systems". Monthly Notices of the Royal Astronomical Society. 520: 761–772. arXiv:2210.02603. doi:10.1093/mnras/stac2847.