Studies of the low-temperature glow left from the Big Bang suggest that several of these "bubble universes" may have left marks on our own.

This "multiverse" idea is popular in modern physics, but experimental tests have been hard to come by.

The preliminary work, to be published in Physical Review D, will be firmed up using data from the Planck telescope.

For now, the team has worked with seven years' worth of data from the Wilkinson Microwave Anisotropy Probe, which measures in minute detail the cosmic microwave background (CMB) - the faint glow left from our Universe's formation.

'Mind-blowing'
 
The theory that invokes these bubble universes - a theory formally called "eternal inflation" - holds that such universes are popping into and out of existence and colliding all the time, with the space between them rapidly expanding - meaning that they are forever out of reach of one another.

But Hiranya Peiris, a cosmologist at University College London, and her colleagues have now worked out that when these universes are created adjacent to our own, they may leave a characteristic pattern in the CMB.

 "I'd heard about this 'multiverse' for years and years, and I never took it seriously because I thought it's not testable," Dr Peiris told BBC News. "I was just amazed by the idea that you can test for all these other universes out there - it's just mind-blowing."

Dr Peiris' team first proposed these disc-shaped signatures in the CMB in a paper published in Physical Review Letters, and the new work fleshes out the idea, putting numbers to how many bubble universes we may be able to see now.

Crucially, they used a computer program that looked for these discs automatically - reducing the chance that one of the collaborators would see the expected shape in the data when it was not in fact there.

The program found four particular areas that look likely to be signatures of the bubble universes - where the bubbles were 10 times more likely than the standard theory to explain the variations that the team saw in the CMB.

However, Dr Peiris stressed that the four regions were "not at a high statistical significance" - that more data would be needed to be assured of the existence of the "multiverse".

"Finding just four patches is not necessarily going to give you a good probability on the full sky," she explained to BBC News. "That's not statistically strong enough to either rule it out or to say that there is a collision."

Dr Peiris said that data from the Planck telescope - a next-generation space telescope designed to study the CMB with far greater sensitivity - would put the idea on a firmer footing, or refute it. However, the data from Planck cannot be discussed publicly before January 2013.

Read more: Microwave background suggests Multiverse theory

According to Brandenburg, the natural explosion, the equivalent of 1 million one-megaton hydrogen bombs, occurred in the northern Mare Acidalium region of Mars where there is a heavy concentration of radioactivity.

This explosion filled the Martian atmosphere with radio-isotopes as well, which are seen in recent gamma ray spectrometry data taken by NASA, he said.

The radioactivity also explains why the planet looks red.

Brandenburg said gamma ray spectrometry taken over the past few years shows spiking radiation from Xenon 129 -- an increase also seen on Earth after a nuclear reaction or a nuclear meltdown, including the one at Chernobyl in 1986 and the disaster in Japan earlier this month.

Dr. David Beaty, Mars program science manager at NASA's Jet Propulsion Laboratory, told FoxNews.com that he finds the idea intriguing and fascinating. But to prove the science, the agency would need to plan a mission to explore Mare Acidalium on Mars.

And there are more pressing issues, including missions to find extraterrestrial life. "You have to assess the importance of the question relative to the cost of answering the question," he said.

Still, Beaty expressed doubts, saying the geological conditions on this planet and Mars have existed for millennia -- what exists has existed for a long time, and there are few sudden changes. "Rocks are what they are. [A natural nuclear reaction] could happen in another billion years, but it is not something to make you want to go home to your family and move to the mountains right away," he said.

Read more: Was There a Natural Nuclear Blast on Mars?

Stargazers can get a great look at Jupiter on any clear night for the rest of September. The giant planet, always bright, will be especially hard to miss as it approaches closer to Earth than it will at any time until 2022.

In North America this month, Jupiter will be low in the east shortly after twilight, moving higher up toward the southeast as the evening grows late, according to NASA and Sky and Telescope magazine.

Jupiter will be nearest to Earth on the night of Monday, Sept. 20, when it passes 368 million miles (594 million km) away. For comparison, the sun is about 93 million miles (150 million km) from us. But viewers shouldn't despair if they miss the show on the 20th: Jupiter will be nearly as close and bright all month.

Earth orbits the sun in about 365 days. But Jupiter, farther out there, takes 4,332 Earth-days to make the same trip. Therefore, Earth laps Jupiter periodically, on the inside track. As that pass occurs, the two worlds come much closer than when they are on opposite sides of the sun. Because the planets' orbits are not perfect circles, some passes are tighter than others.

This Jupiter sky map shows where to look to see the bright planet on the night of Sept. 20.

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Read more: Jupiter to Make Closest Approach to Earth Until 2022