How Much Longer Can Earth Support Life?
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Even if an errant asteroid, nuclear holocaust or other disaster don't doom Earth, in another 1.75 billion years the planet will travel out of the solar system's habitable zone and into a hot zone that will scorch away its oceans.
Jason Ahrns, a graduate student at the University of Alaska-Fairbanks, goes sprite-chasing at night during electrical storms. Here he captures column-shaped red sprites over Red Willow County, Nebraska, on Aug. 12, 2013.
A “jellyfish” sprite photographed over Republic County, Kansas, on August 3, 2013. "I have very good low light eyesight, and I've watched tons of sprites in real time on the context cameras so I know exactly what and where to look. I was watching intently out the window while I snapped these shots, and the camera caught a sprite that I didn't see," writes Ahrns in his blog: http://musubk.blogspot.fr/2013/08/sprites-2013-update-4.html
Like flames from a butane lighter, three blue jets (slightly blurred due to the motion of the aircraft) appear above the lightning-lit clouds in this photo taken over Republic County, Kansas, on August 3, 2013. Ahrns describes this picture as the "the cream of the crop," due to the difficult nature of capturing blue jets. "Since jets tend to hug the top of the clouds it's understandable that they're more difficult for a ground observer to see/photograph, so it makes sense that being up in a sprite-chasing aircraft would give me a serious advantage," he writes.
"Unlike sprites, blue jets aren’t directly triggered by lightning, but seem to be somehow related to the presence of hail storms," reports the Smithsonian: http://blogs.smithsonianmag.com/artscience/2013/08/scientists-capture-rare-photographs-of-red-lightning/.
Red sprite over Canadian County, Oklahoma, on August 6, 2013. "I was also able to see quite a few jets with my naked eyes! That's a first for me, and I'm always excited to see a new sky phenomenon for myself. I still haven't been able to see a sprite naked-eye, and it impresses me just how difficult that actually is," Ahrns writes.
Ahrns' Nikon D7000 on a flexible tripod points out the window of the sprite-chasing aircraft, a Gulfstream V with the National Center for Atmospheric Research. "I butted the camera up against the window glass and put my weight on it to get rid of most of the wobbles and light leaks, but the motion of the aircraft itself still showed up, especially when we hit a patch of turbulence (we are, you know, flying right next to a thunderstorm)," he writes.
Earth could continue to host life for at least another 1.75 billion years, as long as nuclear holocaust, an errant asteroid or some other disaster doesn't intervene, a new study calculates.
But even without such dramatic doomsday scenarios, astronomical forces will eventually render the planet uninhabitable. Somewhere between 1.75 billion and 3.25 billion years from now, Earth will travel out of the solar system's habitable zone and into the "hot zone," new research indicates.
These zones are defined by water. In the habitable zone, a planet (whether in this solar system or an alien one) is just the right distance from its star to have liquid water. Closer to the sun, in the "hot zone," the Earth's oceans would evaporate. Of course, conditions for complex life, including humans, would become untenable before the planet entered the hot zone. (The Top 10 Ways to Destroy Earth)
But the researchers' main concern was the search for life on other planets, not predicting a timeline for the end of life on this one.
The evolution of complex life on Earth suggests the process requires a lot of time.
Simple cells first appeared on Earth nearly 4 billion years ago. "We had insects 400 million years ago, dinosaurs 300 million years ago and flowering plants 130 million years ago," lead researcher Andrew Rushby, of the University of East Anglia in the United Kingdom, said in a statement. "Anatomically modern humans have only been around for the last 200,000 years — so you can see it takes a really long time for intelligent life to develop."
Rushby and his colleagues developed a new tool to help evaluate the amount of time available for the evolution of life on other planets: a model that predicts the time a planet would spend in its habitable zone. In the research, published today (Sept. 18) in the journal Astrobiology,they applied the model to Earth and eight other planets currently in the habitable zone, including Mars.
They calculated that Earth's habitable-zone lifetime is as long as 7.79 billion years. (Earth is estimated to be about 4.5 billion years old.) Meanwhile, the other planets had habitable-zone lifetimes ranging from 1 billion years to 54.72 billion years.
"If we ever needed to move to another planet, Mars is probably our best bet," Rushby said in a statement. "It's very close and will remain in the habitable zone until the end of the sun's lifetime — 6 billion years from now."
While other models have been developed for Earth, they are not suitable for other planets, he added.
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