Mars is Down, Venus is Rising in the Race For Human Space Travel

In the race to put humans on other planets in the Solar System, Mars has been in the lead as of late, but Venus was once the planet of choice. Long called the Sister of Earth or Earth’s Twin because the planets are similar in size, have about the same mass and are made of the same materials, it was thought that the clouds hiding its surface would someday be parted to reveal a paradise where humans could live – perhaps even sharing it with inhabitants of Venus. Mars may have had its canals, but Venus had so much more to inspire mythology and later science fiction writers, who saw it as beautiful as its goddess namesake – a planetary mother that could be inhabited immediately or terraformed into Earth’s tropical planetary vacation spot. Unfortunately, those dreams were shattered when the first probes visited Venus in the 1960s and discovered the realities of its 932 degrees F surface temperature, poisonous dense atmosphere, unbelievable wind speeds, violent volcanoes and more. That was when peaceful Mars (ironic, since it was named for the god of war) moved into first place – even after probes discovered the canals weren’t water-filled. Science explorers and billionaires have turned their focus to the Red Planet … but their plans may be premature as new discoveries about both planets are pushing Venus as the top destination for the next human mission. Will both men and women soon be from Venus?

“Venus gets a bad rap because it’s got such a difficult surface environment. The current Nasa paradigm is moon-to-Mars. We’re trying to make the case for Venus as an additional target on that pathway.”

In an interview with The Guardian, Dr. Noam Izenberg of the Johns Hopkins University Applied Physics Laboratory proposes that a Venus flyby by a human-filled spaceship should be the focus of NASA and other public and private space agencies for a variety of reasons. He begins by acknowledging that this would not be a colonization endeavor because of the atmospheric and surface conditions on Venus, but it would be the easiest way to prove that interplanetary travel by humans is possible and survivable before embarking on a longer, more expensive and potentially more dangerous Mars mission.

“You’d be learning about how people work in deep space, without committing yourself to a full Mars mission. And it’s not just going out into the middle of nowhere – it would have a bit of cachet as you’d be visiting another planet for the first time.”

Izenberg presented his proposal for a mission to Venus at the recent International Astronautical Congress (IAC) in Paris, where he tried to entice dubious scientists with some of the benefits he saw to going to Venus first. For starters, Venus is much closer to Earth than Mars – a mission to the planet and back, with time for observational orbits, could be completed in less than a year. That’s closer to some of the longest stays on the International Space Station, so questions about physical endurance, radiation exposure and psychological issues are minor, if not moot. On the other hand, a Mars mission would last three years – a long time to spend in a ship on a trip where the first crew would most likely not touch down on the planet.

For those who won’t give up on Mars, Izenberg points out that a Venus flyby would also test the idea of using Venus as a gravity-assist slingshot to fling a spaceship to Mars on a much faster trajectory than a direct flight might entail – with the added benefit of fuel savings. Finally, he and presentation partner Alexander Macdonald, NASA’s chief economist, described how a crewed Venus mission could explore the planet without touching down – deploying remote-operated rovers, drones and balloons to the surface to observe active volcanoes, look for water, dig for signs of life and more. Macdonald admits that the idea “doesn’t yet have traction” but that’s why he and Izenberg put together their “Meeting with the Goddess” study and presentation.

If Izenberg and Macdonald need more scientific support to build their case for a ‘Venus first’ human mission, they may have gotten it this week from an unlikely place – Mars itself. One of the selling points for a Mars mission is the fact that orbiters and rovers are finding evidence of frozen and possibly liquid water on or not far below the surface – water that can potentially be used for sustenance, construction and fuel for a return flight. That potential took a big swing to the negative side this week with the publication of a study by Cornell University researchers looking at reflections of what many scientists thought were lakes of liquid water peeking out from under the southern polar ice cap of Mars.

"This result, combined with other recent work, calls into question the likelihood of finding liquid water below the south polar layered deposit (SPLD)."

Researchers led by astronomer Dan Lalich of Cornell University were taking a second look at radar signals first detected a few years ago by the European Space Agency's Mars Express satellite probe which appeared to be reflecting off of a patch of unusually reflective material under the planet’s southern polar ice cap. This was not a one-time anomaly either – additional radar scans detected more of these reflective patches of material at the south pole. Looking for an explanation, researchers at the time turned to Earth’s South Pole region and found similar underground reflective patches in Antarctica that were signs of subglacial lakes like Lake Vostok and other interconnected liquid reservoirs under the polar ice. Following the logic, this must mean that what the Mars Express found was underground caches of liquid water at the south pole of Mars. However, logic doesn’t apply on Mars because the planet is too cold for liquid water. So, what is the reflective material?

“I used CO2 layers embedded within the water ice because we know it already exists in large quantities near the surface of the ice cap. In principle, though, I could have used rock layers or even particularly dusty water ice and I would have gotten similar results.”

Lalich explains in a Cornell press release (the results of his study were published in the journal Nature Astronomy) that he used a one-dimensional modeling procedure to simulate the Martian polar reflections using four materials – atmosphere, water ice, carbon dioxide (CO2) ice and basalt – and looked at their interaction with electromagnetic radiation passing through them. He found that two CO2 layers separated by a layer of dusty ice produced the same reflections as the purported liquid water reflections. As he suggests, rock layers would give the same results. In other words, the material is probably not liquid water. That doesn’t mean there is no liquid water on Mars – just that this isn’t it. Lalich thinks there is only one way to find liquid water on the Red Planet.

“I’m not sure anything short of a drill could prove either side of this debate definitively right or wrong.”

That is putting the water cart before the horse – planetary explorers want proof of the existence of liquid water on Mars as part of the justification to send humans there. If there is no liquid water, that means melting ice – a process that severely complicates colonizing the Red Planet.

Yes, you’re right – Venus doesn’t have liquid water either. However, it is closer … and Izenberg and Macdonald have one more justification up their spacesuit sleeves – visiting Venus for a close look with human eyes will help exoplanetary scientists looking in other solar systems for signs of life better determine what kinds of atmospheres are best suited for supporting it … in forms like ours or forms we haven’t encountered yet.

Would you sign up for a trip around Venus or a trip around Mars? It definitely takes more thought that just reading that "Men are from Mars, Women are from Venus" book.