China Plans to Bring Back Samples of Venusian Clouds

Some time in next 10 years, a Chinese mission aims to do what's never been done before: collect cloud particles from Venus and bring them home. But achieving that goal will mean overcoming one of the most hostile environments in the solar system-the planet's cloaking clouds are primarily made up of droplets of sulfuric acid.

When China unveiled a long-term road map for space science and exploration last fall, its second phase (2028-2035) included an unprecedented Venus atmosphere sample-return mission. As is typical for Chinese space missions, few details were made public. But information in a recent presentation shared on Chinese social media gives us new insight into early mission plans.

The slide shows that the key scientific questions being targeted include the potential for life on Venus, the planet's atmospheric evolution, and the mystery of UV absorbers in its clouds. The mission will carry a sample-collection device as well as in situ atmospheric analysis equipment. The search for life is, in part, due to the interest generated by a controversial study published in Nature Astronomy in 2020 that suggested that traces of phosphine in Venus's atmosphere could be an indication of a biological process.

Venus Sample-Return Mission Challenges

Sara Seager, a professor at the Massachusetts Institute of Technology, led a team to put together a Venus atmosphere sample-return mission proposal in 2022. NASA did not select the proposal, but her team has carried on working, including experiments with concentrated sulfuric acid. Although our DNA cannot survive, we have started to show that [a] growing number of organic molecules, biomolecules, are stable. And so we're envisioning there could be life on Venus," Seager told IEEE Spectrum.

Mission proposals like MIT's offer a window into the daunting technical challenges that China's team is facing. Getting to Venus, entering its thick atmosphere, collecting samples, and getting back into Venus orbit to a waiting orbiter to return the samples to Earth, all come with various challenges. But the potential scientific payoff clearly makes these hurdles worth clearing.

The MIT team proposed a Teflon-coated balloon capable of resisting acid corrosion that would float through the sky without the need for propulsion and the associated fuel and mass. Conversely, China's preliminary render shows a winged vehicle, suggesting it is pursuing a different architectural path.

It would be amazing to get samples in hand to really solve some of the big mysteries on Venus." -Sara Seager, MIT

Rachana Agrawal, a postdoctoral associate at MIT, says a couple of the main challenges are related to operations within the clouds. One is navigating through the dense clouds, typically opaque to visible light. While this isn't critical during sampling, knowing exactly where you are is essential when it comes to using a rocket to return samples, with the rocket needing to enter a precise orbit. On Venus, we don't have GPS in the clouds. The rocket cannot see the stars or the surface, and Venus doesn't have a magnetic field," Agrawal states. One answer would be to set up a satellite navigation system for Venus to assist the mission, adding additional launch and complexity.

An ascent vehicle will be needed to get the sample canister into orbit to rendezvous and dock with a waiting orbiter. A two-stage solid propellant rocket-similar to that planned for Mars sample-return mission architectures-would be one of the simpler options. But operating remotely or autonomously, millions of kilometers from Earth, in unknown conditions, will be exacting.

We don't know much about the atmosphere, so we don't know what the local conditions are. So it could be a very dynamic environment that the rocket has to launch from," says Agrawal, adding that launches on Earth are often scrubbed due to high winds. China's scientists and engineers will need to answer all these questions to pull off its own sample return. It has already demonstrated success with its Chang'e-5 and 6 lunar sample returns. It is set to launch the Tianwen-2 near-Earth asteroid sampling mission in late May this year and is targeting a late 2028 launch for its ambitious Tianwen-3 Mars sample-return mission. The experience and tech from these efforts will be instructive for Venus.

MIT's proposed mission design would require 22 tons of spacecraft, with the ultimate aim of delivering 10 grams of atmospheric samples to Earth. It's likely the Chinese design would offer a similar ratio. However, even such a relatively small amount of material could be revolutionary in our understanding of Venus and our solar system.

I'm superexcited about this," says Seager. Even if there's no life, we know there's interesting organic chemistry, for sure. And it would be amazing to get samples in hand to really solve some of the big mysteries on Venus."