Scientists explain mystery of our 'lemon Moon'

A new accurate map of the Moon has shown that it bulges slightly at one side and is flattened at the top and bottom - but how did it get this way?

It might look like a perfect sphere to you and I but scientists have declared that the Moon is most definitely “lemon-shaped”.

Researchers from the University of California published a new study in the journal Nature that uses advanced laser technology to smooth over the craggy lunar surface (one of the traditional difficulties in accurately measuring the Moon) and concludes that our satellite is "surprisingly distorted".

Like our own planet, the Moon has an equatorial bulge and is slightly flattened on the top and bottom - but unlike the Earth this paunch is only on one side. "Like a lemon with an equatorial bulge,” said Professor Ian Garrick-Bethell, a planetary scientist and author of the study.

However, while the Earth's oblate spheroid nature is explained by the vast rotational forces caused by it spinning around (it turns at a quite staggering rate of around 1000 miles an hour) the Moon barely spins at all - so why is it so lumpy?

Other explanations for the satellite's lemon-shape also have to be thrown out: the Moon is too far away from the Earth to be affected by tidal forces and it has no plate tectonics that might have rucked up its surface.

Boom! and there was Moon: an artist's illustration of the collision between an early Earth and a Mars-sized body.

For an explanation Professor Garrick-Bethell and his team had to return to the formation of the Moon - an event known as 'the Big Splash' which occurred some 4.5 billion years ago: an unknown body around the size of Mars collided with the Earth, flinging up vast amounts of debris that were snared by our planet’s gravity and that slowly coalseced, forming into the Moon we see today.

Shortly after this only the surface of the Moon would have actually been solid – a thin crust floating upon a viscous goop of melted rock. The Moon would also have been much closer to the Earth and spinning faster than it is today as a result of the just-gone planetary impact.

If you combine all these factors together, says the Professor, you have a decent explanation for the Moon's current shape. As it spun and cooled it bulged in the middle like a spinning water balloon (much like the Earth), keeping this shape as the gigantic forces that created it slowly wound down, moving away from the Earth into a much cooler orbit.

The result? A Moon that is 'frozen' in time at the point of its violent creation, lumps and all. It just goes to show that there’s nothing like those wild early years to leave a lasting impression on a body.

Start your day with The Independent, sign up for daily news emails
Life and Style
Steve Shaw shows Kate how to get wet behind the ears and how to align her neck
healthSteven Shaw - the 'Buddha of Breaststroke' - applies Alexander Technique to the watery sport
Arts and Entertainment
The sight of a bucking bronco in the shape of a pink penis was too much for Hollywood actor and gay rights supporter Martin Sheen, prompting him to boycott a scene in the TV series Grace and Frankie
tv
Sport
footballShirt then goes on sale on Gumtree
Voices
Terry Sue-Patt as Benny in the BBC children’s soap ‘Grange Hill’
voicesGrace Dent on Grange Hill and Terry Sue-Patt
Arts and Entertainment
Performers drink tea at the Glastonbury festival in 2010
music
Arts and Entertainment
Twin Peaks stars Joan Chen, Michael Ontkean, Kyle Maclachlan and Piper Laurie
tvName confirmed for third series
Sport
Cameron Jerome
footballCanaries beat Boro to gain promotion to the Premier League
Arts and Entertainment
art
News
ebookA unique anthology of reporting and analysis of a crucial period of history
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Guru Careers: Software Developer / C# Developer

£40-50K: Guru Careers: We are seeking an experienced Software / C# Developer w...

Guru Careers: Software Developer

£35 - 40k + Benefits: Guru Careers: We are seeking a Software Developer (JavaS...

SThree: Trainee Recruitment Consultant / Resourcer

£18000 - £23000 per annum + Commission: SThree: As a Trainee Recruitment Consu...

Ashdown Group: UI Developer - (UI, HTML, CSS, JavaScript, AngularJS)

£25000 - £40000 per annum: Ashdown Group: UI Developer - (UI, JavaScript, HTML...

Day In a Page

Abuse - and the hell that came afterwards

Abuse - and the hell that follows

James Rhodes on the extraordinary legal battle to publish his memoir
Why we need a 'tranquility map' of England, according to campaigners

It's oh so quiet!

The case for a 'tranquility map' of England
'Timeless fashion': It may be a paradox, but the industry loves it

'Timeless fashion'

It may be a paradox, but the industry loves it
If the West needs a bridge to the 'moderates' inside Isis, maybe we could have done with Osama bin Laden staying alive after all

Could have done with Osama bin Laden staying alive?

Robert Fisk on the Fountainheads of World Evil in 2011 - and 2015
New exhibition celebrates the evolution of swimwear

Evolution of swimwear

From bathing dresses in the twenties to modern bikinis
Sun, sex and an anthropological study: One British academic's summer of hell in Magaluf

Sun, sex and an anthropological study

One academic’s summer of hell in Magaluf
From Shakespeare to Rising Damp... to Vicious

Frances de la Tour's 50-year triumph

'Rising Damp' brought De la Tour such recognition that she could be forgiven if she'd never been able to move on. But at 70, she continues to flourish - and to beguile
'That Whitsun, I was late getting away...'

Ian McMillan on the Whitsun Weddings

This weekend is Whitsun, and while the festival may no longer resonate, Larkin's best-loved poem, lives on - along with the train journey at the heart of it
Kathryn Williams explores the works and influences of Sylvia Plath in a new light

Songs from the bell jar

Kathryn Williams explores the works and influences of Sylvia Plath
How one man's day in high heels showed him that Cannes must change its 'no flats' policy

One man's day in high heels

...showed him that Cannes must change its 'flats' policy
Is a quiet crusade to reform executive pay bearing fruit?

Is a quiet crusade to reform executive pay bearing fruit?

Dominic Rossi of Fidelity says his pressure on business to control rewards is working. But why aren’t other fund managers helping?
The King David Hotel gives precious work to Palestinians - unless peace talks are on

King David Hotel: Palestinians not included

The King David is special to Jerusalem. Nick Kochan checked in and discovered it has some special arrangements, too
More people moving from Australia to New Zealand than in the other direction for first time in 24 years

End of the Aussie brain drain

More people moving from Australia to New Zealand than in the other direction for first time in 24 years
Meditation is touted as a cure for mental instability but can it actually be bad for you?

Can meditation be bad for you?

Researching a mass murder, Dr Miguel Farias discovered that, far from bringing inner peace, meditation can leave devotees in pieces
Eurovision 2015: Australians will be cheering on their first-ever entrant this Saturday

Australia's first-ever Eurovision entrant

Australia, a nation of kitsch-worshippers, has always loved the Eurovision Song Contest. Maggie Alderson says it'll fit in fine