Was Venus the first habitable planet in the Solar System? “Venus is like the control case for Earth,” said planetary scientist Sue Smrekar with NASA’s Jet Propulsion Laboratory in 2019, about research suggesting that Venus might have looked like Earth for three billion years, with vast oceans that could have been friendly to life. “We believe they started out with the same composition, the same water and carbon dioxide. And they’ve gone down two completely different paths. So why? What are the key forces responsible for the differences?”
“To unwrap the mysteries of Venus we have to look under the hood at Venus’ interior; it is the engine for global geologic and atmospheric evolution,” said Suzanne Smrekar, principal investigator of VERITAS at JPL -a proposed NASA mission that will attempt to provide answers by transforming our understanding of the internal geodynamics that shaped the planet. “Are Venus and Earth fundamentally unique worlds? Or are the differences between these ‘twins’ only cosmetic? Answering this question is key to understanding what makes other rocky planets habitable and, ultimately, emerge with life.”
Smrekar office at the JPL displays an image of Venus’ surface taken by the Magellan spacecraft –the last mission to study Venus’s surface that ended in 1994– revealing a hellish landscape: a young surface with more volcanoes than any other body in the solar system, gigantic rifts, towering mountain belts, a temperatures hot enough to melt lead, sun-obscuring clouds of sulfuric acid, boiling oceans and air pressure similar to early Earth that has crushed every probe that landed on it’s scorching surface.
“Venus is like this cosmic gift of an accident,” Smrekar says about Earth’s “twin” -a rocky planet similar in size- “You have these two planetary bodies—Earth and Venus—that started out nearly the same, but have gone down two completely different evolutionary paths, but we don’t know why.”
Venus may have been a temperate planet hosting liquid water for 2-3 billion years, until a dramatic transformation starting over 700 million years ago resurfaced around 80% of the planet, according to a September 2019 study led by NASA research scientist,Michael Way that gave new view of Venus’s climatic history and may have implications for the habitability of exoplanets in similar orbits.
Now, the proposed for a 2026 launch, VERITAS Mission (Venus Emissivity, Radio Science, InSAR, Topography & Spectroscopy) could lend insights into our own planet’s evolution and even help us better understand rocky planets orbiting other stars.
VERITAS would orbit the planet and peer through the obscuring clouds with a powerful state-of-the art radar system to create 3-D global maps and a near-infrared spectrometer to figure out what the surface is made of. It would also measure the planet’s gravitational field to determine the structure of Venus’ interior. Together, the instruments would offer clues about the planet’s past and present geologic processes, from its core to its surface.
Window Into Early Earth’s Tectonics
Here on Earth, the rigid crust that envelops the planet is broken into a jigsaw puzzle of tectonic plates atop the mantle. Convection in the mantle helps drive motion of the surface plates. As some plates descend into the interior—a process known as subduction—they melt, and volcanic outgassing releases volatiles (such as water, nitrogen, carbon dioxide, and methane) into the atmosphere.
“The biggest mystery to me is the extent of deformation structures on Venus”—areas of rock on the surface that have buckled under immense geologic pressure—”that could be studied to understand the nature of tectonic activity on the planet,” said science team member Joann Stock, a professor of geology and geophysics at Caltech’s Seismological Laboratory about learning more about the geologic processes on Venus—where the warm crust is a good analogy for early Earth’s, when the tectonic plates were just beginning to form—could offer a valuable glimpse into how these processes began on Earth.
3-D Topographic Maps
Producing high-resolution 3-D topographic maps VERITAS would bring into focus structures that have previously been too small to resolve, added Stock. These structures could include raised topography on both sides of strike-slip faults, like the San Andreas Fault, which is an indicator of major tectonic activity. VERITAS would also look for active surface faulting using something called interferometric deformation maps for the first time beyond Earth.
This artist’s concept shows the proposed VERITAS spacecraft using its radar to produce high-resolution maps of Venus’ topographic and geologic features. Image Credit: NASA/JPL-Caltech
In addition, VERITAS would study vast deformation structures called tessera. These plateau-like features may be analogous to Earth’s continents. A leading theory is that Earth’s continents formed when iron-rich oceanic crust subducted and melted in the presence of water, producing huge volumes of new, less iron-rich continental crust that rose above the ocean.
To determine if Venus’ tessera plateaus formed in a similar way to Earth’s continents, VERITAS would construct the first global multispectral maps of Venus’ surface composition. If their composition resembles that of continental crust, we’d also gain information about Venus’ wetter past.
A Volcanic World?
“Determining whether Venus is actively undergoing volcanic activity and understanding what process is driving it is one of the really exciting questions I’d love to see answered,” said planetary scientist Jennifer Whitten, a VERITAS science team member at Tulane University in New Orleans.
Using its spectrometer, VERITAS would determine which rocks recently formed from erupting magma, before interactions with the atmosphere have had time to change their chemical composition. In addition, the spectrometer would search for hotspots from active eruptions, while the radar instrument would search for active faulting, an indication of tectonic activity.
In getting to know Venus’ volcanoes and the geophysical processes causing them, scientists could also gauge their impact on the planet’s climate and, perhaps, answer another key question: Does the planet’s interior still contain large quantities of water like Earth’s does?
Large Reservoirs of Hidden Water?
Plate tectonics and volcanism don’t just affect how a planet takes shape; they are intimately tied to a planet’s habitability. Plate tectonics strongly affects Earth’s long-term climate by influencing the processes that keep the atmosphere in balance: volcanism, which release volatiles into the atmosphere, and subduction, which recycles volatiles back into the interior. Also, the formation and erosion of Earth’s continents have a major influence on the composition of the oceans and atmosphere. Together, these processes provide the nutrients and a habitable climate for life to thrive.
But what is the delicate geodynamic balance that ultimately makes a planet habitable? Considering the discovery of thousands of exoplanets orbiting stars other than our sun, the answer could inform our understanding of their nature.
The Daily Galaxy, Sam Cabot, via Jet Propulsion Laboratory
Image at top of page: Shows the Moon, Venus, Jupiter, Earth from the ISS