When a top starts to wobble wildly toward the end of a spin, it's because the temporary jolt of energy from your hand that was keeping it rotating is just about completely spent, overwhelmed by the relentless pull of Earth's gravity. But in the vacuum of space, where competing gravitational forces -- from, say a nearby star on one side and a gas giant planet on the other -- can keep that wobble going for eons, it could actually be one of the factors that makes a distant planet more habitable for potential life.
At least that's one finding of new modeling conducted by scientists from NASA, the University of Washington, and Weber State University in Utah.
To be clear, the wobbling that we're talking about with planets takes place on a geologic time scale. Imagine a planet that is tilted on its axis by as much as 30 degrees. But as nearby massive planets pull on it over tens of thousands of years, it gradually shifts to tilt in the opposite direction -- basically an eons-long wobble.
This sounds like a relatively extreme example, especially when you consider that Earth is only tilted relative to other nearby planets by no more than 7 degrees and Pluto, one of the most tilted bodies around, is still only leaning 17 degrees to the side. But scientists report that the orbits of two giant planets around the star Upsilon Andromedae were found to be tilted by 30 degrees relative to each other.
"Planets like these are far enough from their stars that it would be easy to write them off as frozen, and poor targets for exploration, but in fact, they might be well-suited to supporting life," Shawn Domagal-Goldman, an astrobiologist at NASA's Goddard Space Flight Center, said in a release. "This could expand our idea of what a habitable planet looks like and where habitable planets might be found."
OK, but why does a prolonged wobble keep things warmer and generally more habitable? Basically, it comes down to an extreme wobble causing the poles to point directly at the nearest sun more often, melting glaciers and maintaining a store of liquid surface water. The result is that wobbly planets located nearly twice as far from their sun as Earth could be able to maintain water and temperatures that are conducive to life as we know it.
"In those cases, the habitable zone could be extended much farther from the star than we normally expect," said J.C. Armstrong, the lead author of a paper published on the findings in Astrobiology Journal. "Rather than working against habitability, the rapid changes in the orientation of the planet could turn out be a real boon sometimes."
In the past, I've joked that surfing on Titan's far-flung methane lakes could be in our future. But perhaps, if Mars somehow gets pulled into a major wobble, we could soon be surfing those Martian polar ice caps-turned-oceans in a few eons.