Venus might be closer to Earth, but that doesn't make it easier to explore than Mars. For starters, the surface of Venus has the pressure of 92 of Earth's atmospheres, to say nothing of the temperatures — which can reach more than 900 degrees Fahrenheit (500 degrees C), heat that can melt lead. But two NASA scientists, Dale Arney and Chris Jones, suggest we skip the surface altogether and stick to Venus's clouds, according to a report in IEEE Spectrum.

To do so would require big policy changes at NASA, which has been promoting crewed Mars missions as part of its Orion program. But these scientists say that the atmosphere of Venus, explored by an airship, may be more hospitable to human missions. Enter the High Altitude Venus Operational Concept, or Havoc.

"it's a chance to do a practice run... of going to mars." About 31 miles (50 km) above Venus' surface, the gravity is only slightly lower than Earth's, and the atmospheric pressure is about the same. What's more, Venus is better shielded from radiation than Mars — exposure to radiation in Venus' atmosphere would be "about the same as if you were in Canada," Arney told IEEE Spectrum. In other words, floating above Venus' surface is attractive because it's more Earth-like.

The vehicle designed to explore the atmosphere is a helium-filled airship that runs on solar power. The idea is to send a robotic version, followed by a larger, crewed version. The airship would have to be folded up inside a spacecraft to get there, with humans following in a separate vehicle. The plan even includes a suggested space colony, floating in the clouds.

The Venus idea is appealing in part because the planet is closer, and could provide experience with technology that would be necessary to get humans to Mars: habitats for crew members, carbon dioxide processing, aerobraking, and other things required to allow humans survive a trip to another planet. "If you did Venus first, you could get a leg up on advancing those technologies and those capabilities ahead of doing a human-scale Mars mission," Jones told IEEE Spectrum. "It’s a chance to do a practice run, if you will, of going to Mars."