Venus was once like an Earth.

• According to computer models of Venus's historical climate by scientists at NASA's Goddard Institute for Space Studies (GISS) in New York, the planet may have had a shallow liquid-water ocean and habitable surface temperatures for up to 2 billion years.

• The findings, which were published this week in the journal Geophysical Research Letters, were acquired using a model identical to that used to forecast future climate change on Earth.

• "Many of the same tools that we use to model climate change on Earth can be adapted to study climates on other planets, both past and present," said Michael Way, the paper's primary author and a researcher at GISS. "These findings suggest that ancient Venus was a very different place than it is today."

• Today's Venus is a horrible place. It possesses a carbon dioxide atmosphere 90 times thicker than Earth's. There is hardly no water vapor present. At its surface, temperatures reach 864 degrees Fahrenheit (462 degrees Celsius).

• Scientists have long hypothesized that Venus formed from identical materials to Earth but evolved in a different way. NASA's Pioneer mission to Venus in the 1980s first hinted that Venus may have once had an ocean. However, because Venus is closer to the sun than Earth, it receives significantly more sunlight. 

•As a result, the planet's early ocean evaporated, water molecules were shattered by UV light, and hydrogen escaped into space. With no water remaining on the surface, carbon dioxide accumulated in the atmosphere, causing global warming.

• Previous research has demonstrated that the rate at which a planet spins on its axis influences whether or not it has a habitable climate. A solar day on Venus lasts 117 Earth days, while a sidereal day lasts 243 Earth days. Until recently, it was considered that the planet's slow rotation rate required a thick atmosphere similar to that of present Venus. 

• Newer research, however, has revealed that a thin atmosphere, such as that of current Earth, may have achieved the same consequence. That means an early Venus with an Earth-like atmosphere may have rotated at the same rate as it does now.