Earth’s future is certainly bright, just not in the way we’d hoped

the Chicxulub

An impact from an asteroidsimilar to the size that caused the Chicxulub crater would befatal for human life on Earth

While researchers think that the Earth will meet a frazzled and devastated end, along with the

innermost worlds Mercury and Venus that will be gobbled up by the star’s expanding limbs, they have reasoned that for our planet to survive, the entire orbital setup needs to keep a hold of its momentum. Such a feat would also see the outermost planets shuffle in response. “Accordingly, the orbits of all of the planets are going to expand by 50 per cent,” says Schröder. “However, that’s true only if the momentum is conserved. In that case, the orbit of Earth would exceed the maximum solar giant radius by some 25 per cent.” It’s here that some scientists are romancing the idea of an Earth that survives the odds, attempting to find hope that would see humanity beat the rules of the universe. “We could try to steer every asteroid that passes Earth ahead of its orbital movement, then we should gain angular movement to enlarge our orbit well in time,” Schröder suggests. Whether our planet manages to survive or not, it doesn’t really matter – at least when it comes to the future of mankind, thinks Schröder. He believes that the Sun has something else in store for us and our star is looking to present us with it much sooner than the latter stages of its evolution. “In about one billion years, long before [the red giant phase] and more gradually, will come the end of the habitability of Earth,” he tantalisingly tells us. This is the stage between now and when it uses up all of its hydrogen, before swelling into a red giant. In this respect Earth’s future is certainly bright, just not in the way we'd hoped it would be. You’re unlikely to notice it, but the Sun is slowly and ever so slightly picking up in both brightness and size. At the moment, and at a comfortable distance from our star, temperatures are perfect for the existence of liquid water, the region we know as the Goldilocks or Habitable Zone. However, as billions of years pass, what we regard to be a privileged spot in our Solar System will become somewhere that isn’t really the place for life as we know it. This is because, for every billion years that pass, our Sun will be kicking up its power output by around ten per cent, in a race to use up the hydrogen that it finds knocking about its core.
With our star turning up the heat, solar warmth mixes with the gases in the Earth’s atmosphere, shifting the Habitable Zone backwards through the Solar System and towards the outer giants of the system. “That will be enough to drive the climate into a runaway greenhouse state. That is, when all water boils off and temperatures will exceed 100 degrees Celsius [212 degrees Fahrenheit],” says Schröder. Clearly Earth’s future is shaping up to be a global disaster. With no life able to adapt to the abrupt end of cycles of nutrients and life-supporting gases, there’s nothing left to breathe life into its dead surface as even the smallest pockets of water evaporate. Worse still, the brutal treatment dished out by our Sun won’t be over even at this point. It all begins when our planet’s interior breathes a death rattle, turning from a molten liquid to a solid that kills off the magnetic field holding the ozone layer in place. It’s this cloak that makes our planet resilient to the harmful ultraviolet rays that our Sun throws at us. Without it, our planet’s surface would be treated to a bath of high-energy radiation that has already left Mars with its barren landscape that we are learning more and more about. Temperatures will continue to rise for our planet and the gas mark will be well and truly turned up, equating to a rise of more than 140 degrees Celsius (284 Fahrenheit) over the average of around 2.8 billion years from now. Earth will then become host to a climate that bears some similarity to the hellish surface of Venus, long before the red giant phase of the Sun takes hold. With many experts, including American geoscientist Professor James Kasting, thinking that Earth is heading for higher temperatures and devastation all round, there’s a certain urgency to act to escape what would ultimately spell the end of humanity. We know that as the Habitable Zone shifts back, even Mars will get its time in the Sun as our star gets bigger and hotter. The relatively chilly Red Planet will eventually reach a temperature similar to the levels likely to have existed during the Earth’s ice age. Further into the future, when Mars is no longer a valid outpost for future colonisation, we will need to look to the gas giants: Jupiter’s moon Europa and Saturn beckon. The ringed planet in particular could hold the key to our escape in the form of Titan. “In certain ways, Titan is the most hospitable extraterrestrial world within our Solar System for human colonisation,” explains Robert Zubrin, an aerospace engineer advocating the manned exploration of Mars. He has also established the Mars Society, an organisation dedicated to promoting the human exploration and settlement of the Red Planet. When it comes to Titan’s potential, Zubrin refers to its atmospheric mix of nitrogen, methane and ethane with the liquid oceans, lakes and rivers implied by the observations of spacecraft such as Cassini. NASA’s famous orbiter also deployed its Huygens lander on Titan to reveal the first and currently only image of an extraterrestrial moon’s surface. Combined with a Sun that’s continually heating up, this somewhat cooler analogue to Earth could be the answer that the survival of humanity is looking for. However, will we get there before our Sun inevitably expands into us?