The scorching surface of our nearest planetary neighbor, Venus, once had oceans of fluid carbon dioxide that carved out its surface, according to new research.

Venus is very similar to Earth in terms of its size, mass, and chemical makeup, but very dissimilar in terms of its ability to host life: the planet’s surface is hellish, with an atmosphere that would crush human beings and clouds of toxic sulfuric acid over a scorching rocky desert surface, according to Discovery News.

However, scientists believe it once had oceans on its surface, but made of CO2 rather than water. Researchers believe there was enough water in the atmosphere in the past to cover the planet with 80-foot-deep oceans, but Venus was never cool enough for it to descend to the surface in the form of rain. Instead, Venus likely had strange oceans of liquid carbon dioxide, a common substance on the planet.

The atmosphere today is 96.5 percent carbon dioxide, according to lead study author Dima Bolmatov of Cornell University. The CO2 likely existed in a “supercritical” state where it had properties similar to both liquids and gases.

Scientists still don’t know much about supercritical matter, but recent computer simulations suggest it can shift quickly from having gas properties to having liquid characteristics.

Today, atmospheric pressure on the surface of Venus is 90 times that of Earth, and in the planet’s early years, it would have been many times greater, which could have created supercritical carbon dioxide that behaved as a liquid.

This could explain the valleys, riverlike beds, and plains on the surface of the planet.

Researchers speculate that clusters of gas-like CO2 would have resembled soap bubbles covered by a thick layer of liquid.

The next step for researchers is to conduct some experiments to learn more about the shift between gas and liquid properties for supercritical carbon dioxide.

Carbon dioxide is a naturally occurring chemical compound that is composed of two oxygen atoms that are double-bonded to a single atom of carbon. It exists on Earth in gas form with a concentration of 0.04 percent in the atmosphere, where it is considered a trace gas. The gas is given off by plants and algea as part of the carbon cycle. It is considered a greenhouse gas and the emission of it is blamed for recent warming trend on the Earth that threatens to melt ice caps, flood cities, and increase the intensity of storms.

Venus is the second planet from our sun and our closest neighbor, significantly nearer to us than Mars. It takes 224.7 Earth days to orbit the sun, and is the brightest natural object that can be seen in the Earth’s night sky. Its similar size, gravity, and composition cause it to be often referred to as Earth’s “sister planet.”

Venus’ surface temperature is a mean of 863 degrees Fahrenheit, making it the hottest planet of the Solar System — even greater than that of Mercury, the closest planet to the sun, which reaches up to 800 degrees Fahrenheit but has a mean temperature of only around 150 degrees.