this Science for Brothers and Sisters is a series that explores how our siblings influence us, from our money and mental health all the way down to our molecules.we will share these stories over the next few weeks.
If you were to ask which planet in the solar system is Earth’s closest sibling, many would probably point to Mars. It orbits nearby, just a little farther from the sun. It was born at the same time as the earth and has the same material. It is thought that it once had rivers and lakes, and even an ocean. NASA has sent a rover to its surface to help us understand whether life once existed on the Red Planet.
But some planetary scientists will tell you to look in the other direction, at a planet that has been little explored but is actually much closer to Earth in size, appearance, composition, and actual distance…that is, toward Venus.
Scientists who study Venus affectionately call themselves Venusians. They like to call Venus Earth’s twin.
Martha Gilmore is a proud Venusian and professor of earth and environmental sciences at Wesleyan University. In the past, our planet didn’t look that different from its two neighbors, she said.
“If you were an alien visiting our solar system 4 billion years ago, you would see three rocky planets, each with an ocean,” Gilmore said.
These planets – Earth, Mars and Venus – look very different from each other today. The Earth is a temperate blue-green marble transformed by living organisms. Meanwhile, its siblings have migrated to two extremes: Mars is a dry, cold, dusty planet with a paper-thin atmosphere, while Venus, the hottest planet in the solar system, is covered in a thick, even Non-living visitors from Earth would also be quickly destroyed.
That’s no exaggeration: Ten probes have reached the surface of Venus; none lasted more than two hours. The temperature on Venus exceeds 800 degrees Fahrenheit and the pressure is more than 75 times that on Earth.
So what happened to those ancient oceans on our two closest planets?
For planets, size and location matter
Temperature and pressure are what differentiate Venus from Earth. Gilmore said the differences stem from several factors: distance from the sun and the internal heat of the planet itself.
All planets carry a certain amount of heat from birth, Gilmore said, a phenomenon she explained to students over holiday dinner.
“It’s like Thanksgiving. You have a hot potato, you know, a baked potato, and you have peas, and you want to eat that potato, but it’s too hot. But the peas, they’re ready because they’re already coming out Because they are small, they are hot.
Mars is a smaller potato, so it loses heat faster. Venus and Earth are similar-sized potatoes, so they should cool at the same rate.
But there’s something else besides internal heat that keeps Venus warm: the sun. Because Venus is closer to the sun, it receives more energy. The extra energy released over billions of years is a big reason why Venus’ atmosphere became so much more intense than what we experience on Earth.
delicate balance
Gilmore said the atmosphere was like a “comfort blanket.” On Earth, for example, the atmosphere helps keep the planet habitable by protecting life from radiation and keeping the surface at a livable temperature for us humans. of nature and ocean.
“The volcano has to be hot enough and big enough,” Gilmore said, because volcanoes are powered by the planet’s internal heat. These volcanoes spew gases that make up the atmosphere. But once an atmosphere forms, the planet must also be large enough that its gravity can actually “hold on” [that] blanket.
While Mars has similar origins to Venus and Earth, its smaller size means its gravity is not strong enough to maintain the small atmosphere it formed when it had oceans early on. As Mars cooled, its volcanic activity slowed…and eventually ceased.
The problem, Gilmore explains, is that planets actually need volcanoes to constantly replenish their atmospheres, because they’re constantly being lost to space.
“Right now at the top of our atmosphere, there are all kinds of nasty rays that are eroding the atmosphere, like cosmic rays and solar rays,” she said.
As a result, Mars’ atmosphere slowly eroded away—becoming so thin that water could no longer remain liquid on the surface. Some of them escaped into space, and others ended up frozen in ice.
Meanwhile, Venus is so close to the sun that its oceans are boiling. Volcanoes also continue to spew out substances such as carbon dioxide – a potent greenhouse gas.
Earth’s atmosphere also contains carbon dioxide, but our oceans help mitigate its heat-trapping effect by absorbing the excess carbon and eventually converting it into rock. That’s why protecting our oceans is so important, Gilmore said.
“Once you get rid of the ocean, you shut down the main mechanism for storing carbon dioxide in rocks,” Gilmore said. “So it just sits in the atmosphere. The greenhouse effect kicks in and you get a super, super hot blanket.”
A runaway greenhouse effect rendering Venus uninhabitable for life is a concern for scientists studying the effects of climate change. Currently, humans emit 100 times more greenhouse gases into the atmosphere each year than volcanoes emit.
Venus is the nearest exoplanet
Studying Venus allows scientists to understand what the world would be like without carbon sinks. But it also happens to be the closest “Earth-like” planet that researchers know of.
Hundreds of planets discovered outside the solar system are about the same size as Earth and may be habitable. But these planets are so far away that sending spacecraft to survey them won’t be feasible for many generations.
Gilmore said Venus is much closer to us. This is a place we have been to before and can visit again. Earth was scientists’ first data point on a habitable planet, but Venus’ past could give us a glimpse of another planet that was once habitable before it changed forever.
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