The hellish planet that we once called Earth’s “twin” has a curious history. Sometime long ago, conditions on the surface of Venus turned into a runaway greenhouse effect. The result is today a planet where an unprotected spacecraft will get fried and crushed in seconds. How did Venus get to be this way, and is there anything we can learn about global warming on our own planet?
The answers may be in our near future. A fleet of spacecraft is set to make a rare succession of visits to Venus in the 2020s and early 2030s, setting a pace of exploration we haven’t seen at the planet since the 1970s and 1980s.
In that era more than 40 years ago, the Soviet Union sent spacecraft including landers to Venus regularly, and NASA had its own fleet of spacecraft checking out the planet through flybys and orbits.
While other agencies have ventured to planetary orbit in the decades since, it’s been at a slower pace. The acceleration of missions provides a lot of potential to ramp up our understanding of Venus quickly. As an analog, consider Mars — in the past 20 years alone, a swarm of rovers, orbiters and landers from different countries has already taught us much in terms of its atmosphere, water and chances for habitability.
“Just imagine what it would be like, as a [Venus] scientist at the end of the next decade,” Sara Seager, a Canadian scientist who studies Venus at the Massachusetts Institute of Technology, said in an interview. “Then think of how much has happened in 40 years in terms of our understanding of science. Our instruments will be miniaturized. So much has happened, so to … go back and learn more about this enigmatic planet — it’s incredible.”
Seager said scientists have been trying for decades to get a substantial investment in Venus research, and now at least four new missions are being planned for the next decade. For instance, the small rocket company Rocket Lab, with which Seager is involved, plans a tiny private mission in 2023 to probe the planet’s atmosphere in search for life.
Rocket Lab is testing out a new paradigm of space exploration that could, if all goes to plan, encourage the community to send mini-missions every few years to Venus to complement the larger missions funded every few decades, Seager said.
“The first mission [in 2023] would be a very short, very small mission. The payload would be one or two kilograms,” she explained, the small size arising from the diminutive launch mass available on Rocket Lab’s Electron rocket. The payload includes a cruise vehicle along with a miniscule entry probe that will be just big enough to carry one instrument.
“I’m leading the science team for this effort. We have two instruments that we are [considering], and we’ll downselect to one,” she explained. One of the instruments is a mini-tunable laser spectrometer that would have two channels available to search for two kinds of gases. The other options is a miniature UV laser, which would light up the particles in search of the presence of organic molecules, which could indicate signs of life in the atmosphere (as organics, in some cases, indicate the presence of life.)
Rocket Lab’s efforts have been public for a while, but then there were three more announced major missions in the past few weeks.
NASA announced two Discovery-class missions for US $500 million (CA $616 million) each on June 2. DAVINCI+ (Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging) will examine the composition of the atmosphere, search for an ancient ocean, and send down an descent sphere to look at noble gases and other elements to find the origins of the greenhouse effect, among other things. Meanwhile, VERITAS (Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy) will probe the ground with surface aperture radar to, principally, learn more about the planet’s geologic history. These missions will launch between 2028 and 2030, if all goes to plan.
Days later, the European Space Agency said it would also send its first mission to the planet since the Venus Express spacecraft was deliberately thrown into the atmosphere in 2014 — this after extending its mission several times and surviving eight years orbiting Venus. The newly announced orbiting EnVision will give “a holistic view of the planet, from its inner core to upper atmosphere, to determine how and why Venus and Earth evolved so differently,” ESA said in a June 10 announcement. EnVision could launch in 2031.
In September 2020, Seager was part of a science team that announced evidence of phosphine in the cooler atmosphere of Venus. Phosphine could be a marker of life and the molecule was independently confirmed in the team’s observations with the James Clerk Maxwell Telescope in Hawaii, and the Atacama Large Millimeter Array observatory in Chile.
Other teams have been re-examining the data, however; while Seager said her team stands by the measurements it made and also corrected an error in the data, some other members of the community said the presence of phosphine may also indicate natural atmospheric processes (as phosphine could be a result of the sulphur dioxide in the clouds of Venus, for example.)
“You’re watching science evolve in real time,” Seager said of the community discussion. “And these things take a long time to resolve.” An analog discussion is the at least 15-year debate considering the presence of methane on Mars, as measurements from orbit, telescopes and even the Curiosity rover on the planet’s surface have all found different amounts – or sometimes, no methane at all.
Seager said she’s hopeful the DAVINCI+ will have the flexibility to include a phosphine channel on its descent probe, to gather more data from orbit. “I can’t speak with authority since I’m not part of the team,” she cautioned, but said such an up-close measurement could help advance the debate.
This biweekly column by Canadian science and space journalist Elizabeth Howell focuses on a trending news topic in Canadian astronomy and space.