Did the Earth once have two moons ?

[Saru]

It is believed that there was more than one moon in orbit around the Earth shortly after its formation.

The Earth’s moon may once have not been on its own, according to lunar scientists. The smaller ‘twin’ moon is believed to have only survived a few million years before it collided with the one we see today to leave just one.

Read more...

[Bendy Demon]

It's interesting and plausible.

I even had a dream about it once (though it was probably spurned by my reading of a similar article) but in the dream the second moon collided into the earth and broke up because it was really a large mass of loosely combined rocks and dust. (Don't recall reading that though)

However I am not sure if the article pointed out any amount of evidence to support the theory though. (Probably missed that point...)

[spud the mackem]

I guess they have to come up with some theory or other in order to justify their existence.No one knows (or cares} what happened a few million years ago.if I said that the asteroid belt was once a planet,would I be believed ?

[meryt-tetisheri]

The night sky must have been beautiful with two moons shining even if one of them was a lot smaller than the other!

[pallidin]

I read the article, so maybe I missed something, but I don't see what evidence is suggested to support their theory.

[Astral Hillbilly]

Exactly what I was going to post pallidin ! No explanation at all about what makes them think this event happened. Heck, maybe we had 3 moons. 4 moons !

[WhachyJack]

I love what passes as science today. It involves many of the following words and phrases: "could have been", "might have been", "perhaps", "seems to have", "possibly", etc.

[Waspie_Dwarf]

I love what passes as science today. It involves many of the following words and phrases: "could have been", "might have been", "perhaps", "seems to have", "possibly", etc.

That has always been what passes for science. Scientists realise that they are not dealing in absolutes, but are trying to understand how the universe works. They realise that whilst an accepted theory maybe the best fit for the available data, future research may render that theory obsolete.

They also know the difference between a hypothesis and an accepted theory. They know that a hypothesis is a suggestion of what could be. Something to be tested and accepted or rejected depending on whether the evidence supports the hypothesis. They know that "could have been", "might have been", "perhaps", "seems to have" are the correct and honest ways to describe an unproven hypothesis.

I love what passes as commentary on science these days, criticism without comprehension of what good science actually is and the inability to recognise the difference between a newspaper article written by a journalist and a peer reviewed scientific paper.

[Waspie_Dwarf]

I guess they have to come up with some theory or other in order to justify their existence.

It's called research and it is why we have, as a species, accumulated a vast wealth of knowledge.

No one knows (or cares} what happened a few million years ago.

Forgive me spud, I seem to have missed the vote when you got elected to speak for humanity on what everyone cares about.

Just because you neither know or care do not presume that all of us believe that ignorance is bliss.

if I said that the asteroid belt was once a planet,would I be believed ?

Well given you previous statement that no one knows or cares what happened millions of years ago I suspect not. However if you were able to present a compelling case for your argument and back it up with evidence maybe.

[paperdyer]

I read the article, so maybe I missed something, but I don't see what evidence is suggested to support their theory.

Exactly what I was going to post pallidin ! No explanation at all about what makes them think this event happened. Heck, maybe we had 3 moons. 4 moons !

I completely agree. If the two moons were moving at the same speed, they never would have collided. One would have had to be a different speed, even if it was due to gravitational pull from the other.

[coolguy]

This could have been but they really don't know for sure.

It would be cool if we had two moons now

[d e v i c e]

I don't see why we couldn't of had two moons at some stage. Who knows, maybe even three or four smaller ones. Even little Mars has two.

[Waspie_Dwarf]

However I am not sure if the article pointed out any amount of evidence to support the theory though. (Probably missed that point...)

I read the article, so maybe I missed something, but I don't see what evidence is suggested to support their theory.

The article doesn't give an evidence to support the hypothesis. It does say:

The theory will be explained by Professor Erik Asphaug, from the University of California at Santa Cruz at a conference about the moon to be held at the Royal Society this September.

I suspect we will know what evidence Prof. Asphaug has in September.

I did do a quick Google search, and it seems that not many news agencies/papers have run with this story so far (maybe they are waiting until after the conference).

The Australian ran the story (HERE) and it had this paragraph, not found in the Telegraph article Saru linked to:

Evidence of the "twin" is to be found on the dark side of the moon - permanently turned away from Earth - which has mountainous landscapes very different from the smooth face visible on Earth, Professor Asphaug said. He believes those mountains are the remains of the smaller moon, which would have been about one-30th the size of the larger body. "It would have orbited Earth at the same speed and distance and just got slowly sucked in until they hit and then coalesced," he said.

The markedly different nature of the lunar near side and far side has been puzzling astronomers since the far side was first seen in the late 1950s, If I understand correctly Professor Asphaug's hypothesis is an attempt to explain this difference.

[Waspie_Dwarf]

I don't see why we couldn't of had two moons at some stage. Who knows, maybe even three or four smaller ones. Even little Mars has two.

We had a second (natural) moon, albeit temporarily, as recently as 2007. The asteroid 2006 RH₁₂₀ entered Earth orbit in 2006, made 4 orbits and was then ejected again. It's very temporary nature as a second moon means that it is not really regarded as such and is designated an asteroid..

An object called J002E3 was discovered orbiting the Earth in September 2002 and was ejected again in June 2003, however this is believed to be man made, probably the third stage of the Apollo 12 Saturn V mission from 1969. It may enter Earth orbit again in 2032.

Finally there is an object called 6Q0B44E which was discovered orbiting the Earth 2 to 3 times the Moon's distance, taking about 80 days to complete 1 orbit. This, like J002E3, is currently believed to be man made space debris rather than a natural satellite.

[d e v i c e]

We had a second (natural) moon, albeit temporarily, as recently as 2007. The asteroid 2006 RH₁₂₀ entered Earth orbit in 2006, made 4 orbits and was then ejected again. It's very temporary nature as a second moon means that it is not really regarded as such and is designated an asteroid..

An object called J002E3 was discovered orbiting the Earth in September 2002 and was ejected again in June 2003, however this is believed to be man made, probably the third stage of the Apollo 12 Saturn V mission from 1969. It may enter Earth orbit again in 2032.

Finally there is an object called 6Q0B44E which was discovered orbiting the Earth 2 to 3 times the Moon's distance, taking about 80 days to complete 1 orbit. This, like J002E3, is currently believed to be man made space debris rather than a natural satellite.

That's very interesting and eye opening too. Thanks very much Waspie_Dwarf.

[Waspie_Dwarf]

That's very interesting and eye opening too. Thanks very much Waspie_Dwarf.

Apart from J002E3 it was stuff I didn't know either. You learn something new every day.

[shrooma]

have people stopped calling cruithne our `2nd moon` now then....?

poor thing seems to have gone theway of pluto!

'alas poor cruithne, we knew him briefly.....'

:-)

[Waspie_Dwarf]

have people stopped calling cruithne our `2nd moon` now then....?

poor thing seems to have gone theway of pluto!

'alas poor cruithne, we knew him briefly.....'

:-)

Astronomers never did. It is not in Earth orbit so, by definition, is not a natural satellite. It orbits the sun in a resonant orbit with Earth.

[shrooma]

i know they didn't Waspie, i heard the alarm go off every time alan davis mentioned it on QI.....

:-)

[Lex540]

impossible unrealistic

[Waspie_Dwarf]

impossible unrealistic

Would you care to elaborate? Could you share the data you used to come to this conclusion?

As Professor Erik Asphaug (who, incidentally is a leading expert on asteroids, comets and impacts) won't be giving details about his hypothesis until September I don't see how you can discount it as unrealistic when you don't even know what it is you are discounting.

[Jodie.Lynne]

Fascinating theory, I'll have to look Professor Asphaugs paper in September.

Highly likely, in my humble opinion, since the young solar system was full of matter, and small bodies would be accreting loose material and then losing it in collisions with other bodies.

[spud the mackem]

It's called research and it is why we have, as a species, accumulated a vast wealth of knowledge.

Forgive me spud, I seem to have missed the vote when you got elected to speak for humanity on what everyone cares about.

Just because you neither know or care do not presume that all of us believe that ignorance is bliss.

Well given you previous statement that no one knows or cares what happened millions of years ago I suspect not. However if you were able to present a compelling case for your argument and back it up with evidence maybe.

Hi Waspie, Re your reprimand (no hard feelings),I Don't care what happened millions of years ago, because we cannot change it, but I do care about what may happen in the future,just for info I have followed my hero Sir Patrick for over 45 years and still receive the Sky At Night magazine,and have over 40 c.d's on Astronomy,so I do care on certain astronomical events,but please don't "slag off" someone who makes a comment,on an issue which cannot be proven, and never will be.I have noticed that you tend to go into "attack" mode on other peoples comments as well as my own,which is your prerogative.Best wishes.