A new computational analysis, however, shows that a moonless Earth would still have swings in its tilt but the influence of Jupiter and other factors would limit the variations to about 10 degrees in either direction.
Earth's rotational tilt varies between 0.5 and 1 degree about every 100,000 years.
"Plus- or minus-10 would certainly be noticeable and may be a problem, but I don't think it would prevent life from coming about," Barnes said.
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"It's a very intriguing result. It's provocative," Richard Vondrak, lead scientist with NASA's ongoing Lunar Reconnaissance Orbiter mission, told Discovery News.
"On the moon we can find important evidence and clues of what happened to not only the moon, but also to the Earth-moon system over the last 4.5 billion years," said Vondrak, a planetary scientist with NASA's Goddard Space Flight Center in Greenbelt, Maryland.
The study also showed that if Earth revolved around the sun in the opposite direction, called a retrograde orbit, it wouldn't need a moon at all to have a climate about as stable as it has today. Likewise, a Jupiter about half the distance to Earth as its present location would have had a similar steading hand, Barnes added.