NASA Climate Modeling Suggests Venus May Have Been Habitable

NASA | AUGUST 16, 2016

Venus may have had a shallow liquid-water ocean and habitable surface temperatures for up to 2 billion years of its early history, according to computer modeling of the planet’s ancient climate by scientists at NASA’s Goddard Institute for Space Studies.

Observations suggest Venus may have had water oceans in its distant past. Image credit: NASA

Venus today is a hellish world. It has a crushing carbon dioxide atmosphere 90 times as thick as Earth’s. There is almost no water vapor. Temperatures reach 864 degrees Fahrenheit (462 degrees Celsius) at its surface.

Scientists long have theorized that Venus formed out of ingredients similar to Earth’s, but followed a different evolutionary path. Measurements by NASA’s Pioneer mission to Venus in the 1980s first suggested Venus originally may have had an ocean.

However, Venus is closer to the sun than Earth and receives far more sunlight. As a result, the planet’s early ocean evaporated, water-vapor molecules were broken apart by ultraviolet radiation, and hydrogen escaped to space. With no water left on the surface, carbon dioxide built up in the atmosphere, leading to a so-called runaway greenhouse effect that created present conditions.

Previous studies have shown that how fast a planet spins on its axis affects whether it has a habitable climate. A day on Venus is 117 Earth days. Until recently, it was assumed that a thick atmosphere like that of modern Venus was required for the planet to have today’s slow rotation rate.

However, newer research has shown that a thin atmosphere like that of modern Earth could have produced the same result. That means an ancient Venus with an Earth-like atmosphere could have had the same rotation rate it has today.

Another factor that impacts a planet’s climate is topography. Ancient Venus had more dry land overall than Earth, especially in the tropics. That limits the amount of water evaporated from the oceans and, as a result, the greenhouse effect by water vapor.

This type of surface appears ideal for making a planet habitable; there seems to have been enough water to support abundant life, with sufficient land to reduce the planet’s sensitivity to changes from incoming sunlight.

The study also factored in an ancient sun that was up to 30 percent dimmer. Even so, ancient Venus still received about 40 percent more sunlight than Earth does today.

In the model, Venus’ slow spin exposes its dayside to the sun for almost two months at a time. This warms the surface and produces rain that creates a thick layer of clouds, which acts like an umbrella to shield the surface from much of the solar heating. The result is mean climate temperatures that are actually a few degrees cooler than Earth’s today.

YOU MAY ALSO LIKE

K2 Finds Dead Star Vaporizing a Mini 'Planet'

Scientists have uncovered strong evidence of a tiny, rocky object being torn apart as it spirals around a white dwarf star. This discovery validates a long-held theory that white dwarfs are capable of cannibalizing possible remnant planets that have survived within its solar system.

NASA Spacecraft Achieves Unprecedented Success Studying Mercury

After extraordinary science findings and technological innovations, a NASA spacecraft launched in 2004 to study Mercury will impact the planet’s surface, most likely on April 30, after it runs out of propellant.

The Strange Structures of the Saturn Nebula

The spectacular planetary nebula NGC 7009, or the Saturn Nebula, emerges from the darkness like a series of oddly-shaped bubbles, lit up in glorious pinks and blues.

Cassini Spies Titan's Tallest Peaks

Titan's tallest peak is 10,948 feet (3,337 meters) high and is found within a trio of mountainous ridges called the Mithrim Montes. The researchers found that all of Titan's highest peaks are about 10,000 feet (3,000 meters) in elevation.

The Mysterious 'Lakes' on Saturn's Moon Titan

Saturn's moon Titan is home to seas and lakes filled with liquid hydrocarbons, but what forms the depressions on the surface? A new study using data from the joint NASA and the European Space Agency Cassini mission suggests the moon's surface dissolves in a process that's similar to the creation of sinkholes on Earth.

Spitzer Maps Climate Patterns on a Super-Earth

Observations from NASA's Spitzer Space Telescope have led to the first temperature map of a super-Earth planet -- a rocky planet nearly two times as big as ours.