The latest overview of the VERITAS mission was published by NASA's Jet Propulsion Laboratory (JPL) on July 8, 2020.
VERITAS - Venus Emissivity, Radio Science, InSAR, Topography & Spectroscopy - is one of the four proposed missions being considered for NASA's Discovery Program. Suzanne Smrekar, VERITAS principal investigator at JPL, stated:
Venus is like this cosmic gift of an accident. You have these two planetary bodies, Earth and Venus, which started almost the same way, but have gone two completely different evolutionary paths, but we don't know why.
Artist's concept of the active volcano on Venus, and a subduction zone, where a tectonic plate on the surface sinks inside the planet. Image via NASA / JPL-Caltech / Peter Rubin.
Venus is a rocky world like Earth, but its surface is completely obscured by a thick, dense atmosphere of carbon dioxide. Surface temperatures never drop below 900 degrees Fahrenheit (500 degrees Celsius), and the pressure, similar to that of Earth's oceans, would quickly crush humans. The clouds contain sulfuric acid. It is not exactly the most hospitable place in the solar system, although higher in the atmosphere, temperatures and pressures are much milder.
VERITAS would look through the dense clouds with radar and a near-infrared spectrometer to create global 3-D maps of the planet and analyze what the surface is made of (we already know that most of the surface is volcanic basalt). By measuring the gravitational field of Venus, VERITAS could also determine the structure of the planet's interior. VERITAS would provide the most detailed analysis of Venus ever obtained by an orbiting spacecraft.
If selected, VERITAS will launch sometime in 2026.
An example of tile warp terrain (white terrain on the right side of the image) on the western edge of Maxwell Montes on Venus. Image via NASA / JPL / Wikipedia.
Scientists are keen to learn more about Venus, to understand why it changed so dramatically. This could also offer new insights into Earth's own evolution as a planet, as well as other rocky planets orbiting other stars.
VERITAS will study the geology of Venus and the similarities it may have with that of the early Earth. The planet's warm crust is believed to be a good analog to that of Earth a few billion years ago, when tectonic plates were just beginning to form. Did the same thing happen on Venus? According to Joann Stock, a geologist and geophysicist at the Caltech Seismology Laboratory in Pasadena:
The biggest mystery to me is the extent of the deformation structures on Venus that could be studied to understand the nature of tectonic activity on the planet.
Deformation structures are areas of rock on the surface that have bent under immense geological pressure. On Earth, the outer crust is divided into tectonic plates that sit on top of the mantle. Some plates descend downward in a process called subduction, caused by convection in the mantle. As the temperature increases as it progresses, those plates begin to melt. This releases volcanic gases and other materials called volatiles, including water, nitrogen, carbon dioxide, and methane, into the atmosphere.
Map of the extensive tile terrain on Venus (white outlines). Image via USGS Astrogeology Science Center / Sjoh197 / Wikipedia.
Could deformation structures be a form of tectonic plates similar to those of early Earth? VERITAS would help scientists answer that question. 3-D topo maps could see much smaller features than was previously possible with previous missions. You could identify landslide faults, similar to the San Andreas fault in California, by looking at the elevated topography on either side of the fault. If VERITAS found such formations, that would be evidence of substantial tectonic activity on the planet in the past, and perhaps even today. VERITAS would also use interferometric deformation maps, using interferometry, to search for active faults on the planet's surface, something that has never been done anywhere other than on Earth before.
If plate tectonics were confirmed on Venus, it would be an exciting discovery, as Earth is the only planet in our solar system that has that kind of geological activity. (Europa, Jupiter's moon, is now believed to have a more primitive form of plate tectonics, but Europa's crust is made up of water ice, not rock.)
The largest and most widespread deformation structures on Venus are called tesserae, plateau-like regions that may be analogous to the continents of Earth. VERITAS would study their composition, to see if they formed similarly to the continents on Earth. That could provide valuable clues to the ancient oceans that many scientists believe once existed on Venus, Earth's continents are believed to have formed when the iron-rich oceanic crust subducted and melted in the presence of water.
Perspective view of the Maat Mons volcano on Venus, based on radar images of Magellan. The volcano is 5 miles (8 km) high. Image via PD / USGOV / NASA / Wikipedia.
What about volcanism? Volcanism is highly intertwined with plate tectonics on Earth. We already know that Venus has many volcanoes, but are any of them still active? There is currently tentative evidence of volcanoes still active on Venus, but it is not yet fully confirmed. VERITAS could help do that. Jennifer Whitten, a member of the VERITAS scientific team at Tulane University in New Orleans, said:
Determining if Venus is actively experiencing volcanic activity and understanding what process it is driving is one of the really exciting questions I'd love to see answered.
VERITAS could search for active eruption hot spots using its spectrometer, and radar could detect active faults, which would be evidence of current tectonic activity. The spectrometer could also detect rocks that had formed from hot magma, before the rock's chemical composition had been altered by the corrosive atmosphere. Knowing how geologically active Venus is or not would also help scientists determine how much water is inside the planet.
Venus geology, plate tectonics in particular, is also important to understand in terms of habitability. The planet's surface may be extremely inhospitable now, but it was not always so. Plate tectonics and volcanism have played an important role in the habitability of the Earth, where plate tectonics helps to keep the climate stable in the long term (apart from human-caused climate change). Volcanism releases volatiles into the atmosphere, while subduction recycles them back into the planet. This continuous cycle keeps the atmosphere in balance. The composition of the atmosphere and oceans is affected by the formation and erosion of the continents, which provide the nutrients necessary for life.
Suzanne Smrekar, VERITAS principal investigator at JPL. Image via Keck Institute for Space Studies.
Smrekar said:
To unravel the mysteries of Venus we have to look under the hood at the interior of Venus; It is the engine of global atmospheric and geological evolution. Are Venus and Earth fundamentally unique worlds? Or are the differences between these 'cufflinks' just cosmetic? Answering this question is key to understanding what makes other rocky planets habitable and ultimately emerge alive.
The last spacecraft to study the surface of Venus from orbit was Magellan, whose mission ended in 1994. If selected as a mission, VERITAS will revolutionize our understanding of how Venus formed and evolved, and why our sister planet changed so dramatically from a habitable world to one that could well have been forged in hell itself.
Bottom line: The proposed VERITAS mission would study the complex geology of Venus.
Via Jet Propulsion Laboratory
