The moon could have formed within just five hours of a colossal collision that rocked the early solar system 4.5 billion years ago, scientists suggest.
For decades, experts have believed the moon was created when a Mars–sized planet named Theia smashed into a young Earth, blasting huge amounts of molten rock into space.
This material was thought to have gradually clumped together over years to form our lunar satellite.
But a team from the Southwest Research Institute and the University of Arizona say there may be another possibility.
Using powerful computer simulations, the researchers discovered that in some scenarios, a largely intact moon emerged astonishingly quickly after the crash.
The deciding factor appeared to be temperature.
‘Depending on how hot the Earth and Theia are prior to the collision, an impact can destroy Theia and produce this massive disk of debris that eventually forms the moon,’ Dr Adeene Denton said.
‘But when I used the same parameters as original impact modelling – down to the equal temperature structures inside both bodies – within around five hours, an intact moon emerged.’
The researchers discovered that in some scenarios, a largely intact moon emerged astonishingly quickly after the crash – in as little as five hours
The team discovered that the geological properties of the colliding worlds play a crucial role in what happens after the impact.
Previous models largely treated the planets as fluid–like bodies and ignored the strength of their rocks.
When the scientists factored in the strength of planetary materials and their temperature, they found dramatically different outcomes.
Hotter planets are weaker and more easily torn apart, they said.
However cooler worlds are stronger and more likely to survive the impact in one piece.
‘Models have evolved to include material strength, something that’s really important when you’re studying collisions between smaller bodies like asteroids or for my previous paper about the formation of the Pluto–Charon system,’ Dr Denton said.
‘We weren’t sure if it would matter for the moon or not.
‘When we did the simulations, we found it actually matters quite a bit.’
When the scientists factored in the strength of planetary materials and their temperature, they found dramatically different outcomes
The findings could help explain some of the moon’s unusual characteristics, including the amount of volatile materials it contains
The findings, published in Astrophysical Journal Letters, could help solve one of the biggest mysteries in planetary science – exactly when the moon–forming impact occurred.
Researchers say the work could also help explain some of the moon’s puzzling characteristics, including differences in its composition and the amount of volatile material it contains.
Dr Robin Canup, who carried out an earlier study on the moon’s origin, said: ‘These surprising and exciting new results imply a potential connection between the physical properties of the moon today, including perhaps its volatile content, and the thermal state of the Earth and Theia at the time of the giant impact.
‘This in turn might help scientists better constrain when the Moon–forming event occurred.’
The researchers said explaining the close compositional makeup of the Earth and the moon remains an open scientific question.
A possible explanation is that Theia and a young Earth formed from a common region of the protoplanetary disk – a pancake–like ring of dense gas and cosmic dust.
Mars, on the other hand, is compositionally different from the Earth and the moon, which indicates it initially formed further away.
‘Because Earth and Mars formed in the same neighbourhood of the solar system, they are like siblings,’ Dr Denton said. ‘The moon and Earth are like fraternal twins.’
Last month, an out–of–control SpaceX rocket smashed into the moon, leaving a visible crater.
The Falcon 9 second stage careened into the lunar surface at 5,400 miles per hour (8,690km/h).
Scientists believe that the 9,920lb (4,500kg), 39ft–long (12m) rocket would have hit with a force equivalent to 15,000 sticks of dynamite, or three tonnes of TNT.
A NASA satellite captured pictures showing the result of the impact – revealing a 60–foot–wide (18m) crater surrounded by streaks of lunar rock thrown up by the rocket’s impact.
WHO HAS BEEN TO THE MOON?
In total 12 people have walked on the moon.
1 + 2. Apollo 11 – July 21, 1969
Neil Armstrong made history by becoming the first person to set foot on the lunar surface, before he he was followed by crewmate Edwin ‘Buzz’ Aldrin.
3 + 4. Apollo 12 – November 19 and 20, 1969
Pete Conrad and Alan Bean were the moon walkers on the Apollo 12 mission.
The Apollo 12 crew experienced two lightning strikes just after their Saturn V rocket launched.
5 + 6. Apollo 14 – February 5, 1971
Alan Shepard and Edgar Mitchell were part of the Apollo 14 mission. They launched on January 31, 1971, and landed in the Fra Mauro region of the moon, the original destination for Apollo 13.
7 + 8. Apollo 15 – July 31, 1971
Dave Scott and James Irwin landed on the moon and stayed for three days, until August 2.
9 + 10. Apollo 16 – April 21, 1972
John Young and Charlie Duke were the next men to walk on the moon. When the crew reached lunar orbit, the mission almost had to be aborted because of a problem with the command and service module’s main engine.
11 + 12. Apollo 17 – December 11, 1972
The final people to walk on the moon were Eugene (Gene) Cernan and Harrison (Jack) Schmitt.
Before he left the moon, Cernan scratched the initials of his daughter Tracy into the lunar regolith. Since the moon does not experience weather conditions like wind or rain to erode anything away, her initials should stay there for a very long time.
All the men who have been to the moon
