Venus is rocky and has roughly 82% the mass and 90% the surface gravity of Earth. It also has a persistent atmosphere and orbits in the sun's "habitable zone" (where water can exist as a liquid). Some researchers think the planet once had warm, shallow oceans that were cozy to life for about 2 billion years. That could be about 1.2 billion years long enough for life to emerge and thrive, if you're using Earth as a scorecard.
And yet its water vanished, carbon dioxide began clogging up the atmosphere, and — due to runaway global warming — the world was cooked to a crisp.
In short, Venus today is just about the worst place imaginable to visit in the solar system, and simultaneously an important analog to better understand our own planet.
We know this thanks to nearly two dozen successful missions there, including eight orbiters and 10 landers, most of them launched by the Soviet Union.
Data beamed back by these spacecraft show Venusian surface air is nearly 97% carbon dioxide, about 100 times thicker than Earth's atmosphere, and is a blistering 864 degrees Fahrenheit (462 degrees Celsius). That's twice the temperature needed to ignite wood and hot enough to melt lead.
But what it's actually like to be on the surface, and what happens to materials and spacecraft that dare land there, hasn't been clear until GEER came along.
What the surface of Venus is like
GEER pulls together everything researchers have learned to date about surface conditions on Venus into an 800-liter chamber. A mixing machine combines the known gases on Venus and a powerful heater warms them up.
"It takes two-and-a-half days to warm up and five days to cool down," Leah Nakley, GEER's lead engineer, told Business Insider.