The short answer is: we don’t know. But the noble gases in Venus’ atmosphere — helium, neon, argon, krypton, xenon and radon — could tell a story about water on the planet, and how quickly it may have disappeared.
As part of DAVINCI+’s mission, the spacecraft will drop a sphere through Venus’ atmosphere to measure these non-reactive gases. Based on what it finds, different levels of noble gases could help scientists flesh out their ideas about Venus’ past habitability and evolution.
“Noble gases and their isotopes — and the abundance of those isotopes — give you a very clear indication of the interior properties of the planet,” Paul Byrne, a planetary geologist at NC State University, told The Planetary Society. “The idea is that if you’re able to measure the noble gas abundance and ratios of these different isotopes, you can draw indirect — but critical — information.”
DAVINCI+’s investigation into Venus’ noble gases will raise a host of questions. How much water might Venus have started out with? How much of that water may have evaporated into the planet’s atmosphere? Was Venus enveloped in magma, even in its early days? Or could some cataclysmic event have caused the planet’s carbon dioxide to escape into the atmosphere, triggering a greenhouse effect?
We’ll have to wait and see what DAVINCI+ and VERITAS dig up.
Despite being a very old planet, Venus is relatively young on the outside. Maps created by NASA’s Magellan spacecraft suggest that about 500 million years ago, the planet underwent some sort of “resurfacing” that changed its exterior.
So what’s the secret to Venus’ youthful glow after 4.5 billion years? It could be volcanoes, but we can’t be sure. Although there’s evidence that volcanism has played an important role in Venus’ past, we know surprisingly little about present volcanic activity on the planet. In fact, active volcanism on Venus has never been directly imaged.
This is one area where DAVINCI+ and VERITAS will be critical. They’ll tie together the story of Venus’ volcanoes, its noble gases and potentially, its watery past. VERITAS in particular will analyze the planet’s infrared surface emissions to search for signs of past or present volcanic activity. The mission will also catalog different rock types, which could point to more evidence of recent or active volcanoes.
“A massive question is: was there some sort of catastrophic event, or more ongoing, steady volcanism that was more Earth-like?” NASA astronomer Sue Smrekar, VERITAS’ principal investigator, told The Planetary Society. “We’ll be able to determine what’s in the bottom of 80% of the craters which have dark floors. Is it volcanism?”
Smrekar and her team will also search for signs of active volcanoes spewing out water. Such a discovery could completely change our understanding of Venus’ interior.
“There’s this old idea that Venus’ interior is dry,” Smrekar said. “But Venus appears to be less outgassed than the Earth. It could have more water in its interior than Earth.”
Where are Venus’ tectonic plates?
Venus is full of strange little surprises; despite being peppered with volcanoes, it doesn’t appear to have plate tectonics.
On Earth, lighter tectonic plates shift beneath heavier ones in a process known as subduction, influencing both earthquakes and volcanoes. So how can Venus have so many volcanoes if it doesn’t have one of the key ingredients to creating them?
Both DAVINCI+ and VERITAS will probe this question, but DAVINCI+ will take the first-ever high-resolution images of some of the planet’s most fascinating features: heavily deformed regions called tesserae.