HIGHLIGHTS
Climate change and
global warming cause
wildfires, droughts, and
more intense storms.
Impacts from space can
block sunlight for months.
A planet’s star can
expand and engulf it.
Some planets survive
being swallowed up by
its star.
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Your bags are packed, your spaceship is fuelled up. It’s time to leave your home world behind. You give a passing thought to those who are choosing to stay, determined to survive the onslaught. Are they sufficiently protected to survive the looming disaster? Will they be able to adapt to what comes next? Time will tell.
Planets don’t exist forever, at least not in their present form. They may undergo extreme climate changes, be slammed by asteroid impacts, or they can be swallowed up by their host stars. Disasters don’t always mean the end, but they do catalyze change.
Climate change is a global threat that is menacing our home planet. While changes in climate patterns can have natural causes, scientists have determined that since the 1800s human activity has dramatically increased global warming. The burning of fossil fuels generates greenhouse gasses that act like a blanket wrapped around the Earth. The gasses trap the Sun’s heat and cause temperatures to rise. The result is melting sea ice and glaciers, which in turn cause the sea levels to rise. We’re also experiencing intense heat waves that spark more frequent wildfires and droughts, and an increase in the duration and intensity of tropical storms. The effects of global warming are especially felt in the Arctic; scientists estimate that by the summer of 2035 it will be free of ice.
To better understand greenhouse effects, scientists are examining other planets in our solar system. Venus, for example, has a very strong greenhouse effect. Its dense atmosphere is mainly made up of the greenhouse gas carbon dioxide, which traps so much heat that the planet’s surface temperature is about 460°C (hot enough to melt lead!). The atmosphere of Saturn’s moon Titan contains a lot of methane, another greenhouse gas, but because it is so far away from the Sun, its surface temperature is only -180°C. The study of the atmospheres of other planets can give us clues about global warming on our home world.
Impacts from space can also spell disaster for a planet. Just ask the dinosaurs – no, wait, you can’t! About 65 million years ago an asteroid called the Chicxulub impactor slammed into Earth with such force, that it left behind a 180 km wide crater near Mexico’s Yucatan peninsula. Dust from the explosion was thrown into the Earth’s atmosphere and blocked sunlight for several weeks, maybe months. The lack of light and warmth killed off most plants and severely disrupted the food chain. Dinosaurs and almost three-quarters of all life on Earth were wiped out.
There is another threat to our planet, though it will take a while until we have to worry about it: stellar evolution. In about 5 billion years our Sun will expand into a red giant star. That means that its diameter will expand by about 150 million kilometers, swallowing the planets Mercury, Venus, and possibly the Earth. It’s going to get pretty toasty. However, not all is lost. There are exoplanets that survive being sun-baked. Nicknamed Salamander planets after the fire-loving mythical lizard, they survive being enveloped by the outer layers of their host stars. Examples of this are three planets orbiting the pulsar PSR B1257+12, even though scientists are scratching their heads trying to figure out how this is possible.
Close proximity to host stars tends to be hazardous for most planets, even the very large ones. When a gas planet’s orbit drifts too close to its host star, the planet’s atmosphere gets siphoned off by the sun’s massive gravitational pull. After a while, the gas planet’s atmosphere is completely stripped away and only its heavy, solid core is left behind. These “planet skeletons” are called Chthonian Worlds, named after the ancient Greek gods dwelling in the Underworld.
Despite the many types of catastrophes that may befall them, planets can be very resilient. There are many ways to die – and many ways to survive.
Osiris: The Chtholian exoplanet
The surface temperature of scorched Osiris is about 1,000°C. It is thought to be the solid remnant core of an evaporated gas giant. Venus, Earth, and Mars may have lost their entire original atmospheres during the early part of their lives, too, so these planets are of great interest to planetary scientists.
Find out more about Osiris
Climate Change Effects
Effects that scientists had long predicted would result from global climate change are now occurring, such as sea ice loss, accelerated sea level rise, and longer, more intense heat waves. They are irreversible on the timescale of people alive today and will worsen in the decades to come.
Find out more from NASA
The Impact That Wiped Out the Dinosaurs
An asteroid roughly 10 km across hit Earth about 65 million years ago. Debris from the explosion was thrown into the atmosphere, severely altering the climate. It wiped out the dinosaurs and about 75% of all life on Earth.
Read more
HABITABILITY
The key ingredient to habitability in a disaster scenario is time. Is the disaster unfolding slowly, measured in millions of years, like the expansion of a star? In that case, organisms will have the time to adapt to their environments. However, evolutionary change typically takes millions of years unless there is outside intervention. Is the disaster a sudden event, like an asteroid impact? Then a solution needs to be deployed faster.
Maybe a way can be found to avert the disaster. In that case, a version of the status quo can be maintained. An asteroid can be diverted, or a population can shelter underground for a while. Nothing exposes the relationship between organisms and the environment more than when the environment is put under stress.
STORY IDEAS
The main theme in a disaster scenario is: do you stay or do you go?
Is there a way to avert the disaster? Can you create a shelter? Can you adapt in some way?
Or do you leave? How? What can you save, and what do you have to sacrifice?
In the expanding sun scenario, the habitable zone will be pushed outwards. For example, in our solar system, the current habitable zone stretches from just inside the orbit of the Earth to the orbit of Mars. Once the Sun turns into a red giant, this zone will shift to the orbits of Jupiter and Saturn. The gas giants’ many moons may become perfect environments for life to develop. And since stellar evolution takes millions of years, there would be enough time to prepare for the journey to a new home.