In planetary science circles, Venus is all the rage now

Extrasolar planets are constantly stealing the scientific thunder of some of our nearest planetary neighbors. But if there’s a trend at this year’s Europlanet Society (EPSC) Congress, it’s the unmistakable increase in resources for future missions to Venus, our infernal companion on the planet.

A slew of new surface and orbital missions to be launched by NASA, the European Space Agency (ESA), India and China are creating a level of new excitement about Venus exploration that has not been seen since the visit of NASA’s Magellan radar cartograph disappeared from the planet in 1990 and ESA’s Venus Express began orbiting the planet in 2006.

There are two main drivers behind all of this activity. One is that if we are ever to understand extrasolar planetary systems like ours, we must understand our infernal neighbor with extraordinarily high surface temperatures and pressures. And second, a better understanding of the ravages of climate change here on Earth. We need to understand what went wrong on Venus to improve our own long-term atmospheric models.

Equipped with instruments such as radar imaging, radioscience and gravity measurements, NASA will launch its VERITAS (Venus Emissivity, Radio Science, InSAR, Topography & Spectroscopy) orbiter mission in November 2027. She is scheduled to arrive on the planet nine months later.

Scientists will use VERITAS data to create the first global, high-resolution maps of radar imagery and topography, NASA says. Surprisingly, planetary scientists still use Magellanic data. But veritas will take radar imaging of the surface of Venus to the next level.

The VERITAS spacecraft will first be launched into the very elliptical orbit of about 30,000 km and will then perform an aerodynamic braking maneuver for about a year. It will then enter a final scientific orbit between 180 and 250 km by 2031. Thus, its nominally two-year full scientific operation will only begin about 2.5 years after launch.

VERITAS will create the first maps of surface rock composition and constrain surface weathering by peering through the planet’s dense atmosphere via infrared spectral windows, NASA says. The mission will also look for thermal and chemical signatures from both recent and active volcanism.

NASA notes that three of the VERITAS science drivers are: What geologic processes are currently active on Venus? What is the size and condition of the core? And if there is water deep inside Venus, does volcanism release it into the atmosphere?

To maximize its surface mapping of Venus’ topography with very high fidelity, VERITAS will use a different radar wavelength than Magellan. Unlike the Magellan mission, which used S-band radar, Veritas will use X-band radar, Scott Hensley, a radar scientist at NASA’s Jet Propulsion Laboratory and project scientist for the VERITAS mission, told me here in Granada. Magellan’s S-band radar had a wavelength of about 12 centimeters, he says. We’re X-band, so we’re about four centimeters in wavelength, Hensley says.

Why does this matter?

In general, people don’t want to use X-band on Venus because you lose so much energy in the atmosphere, Hensley says. But we paid for the atmospheric loss by making sure we could do X-band so we could get a very accurate topographical map, he says.

In terms of resolution, VERITAS will be quite a bit better than Magellan.

There are two types of solutions you might be interested in, says Hensley. The obvious is spatial resolution; how well you can separate things on the surface. The other is radiometric resolution, a measure of how fine the gray levels are on the surface, Hensley says. That gives you more contrast and substance in the data, he says.

To illustrate the difference between Magellan’s radar resolution and VERITAS’ predictions, Hensley presented a 20-kilometer resolution simulation of the large island of Hawaii as if seen by Magellan. It looked a bit like a fuzzy blob. Veritas, on the other hand, will image up to a spatial resolution of 250 meters. That’s two orders of magnitude better than Magellan, says Hensley.

With repeated orbital passes of the planet, VERITAS will be able to combine the data from two passes to measure whether the surface has moved, Hensley says. We’ll be able to determine if a volcano spreading beneath the surface is causing the terrain to bulge, he says.

Was Venus ever habitable?

We want to know if water was present in the past, says Hensley, but determining when the water was much more difficult. But we hope to be able to determine whether water was involved in the formation of continent-like features on Venus called tesserae, he says.

Rising precipitously about two to four kilometers above the planet’s surrounding plains, these highly deformed parts of the surface are thought to be the planet’s oldest geologic units. They manifest themselves as circular highland plateaus up to 2500 km in diameter. These so-called “Tesserae Terrains” dominate the plateaus of Venus; cover about 8 percent of the earth’s surface.

Because these areas are thought to be among the oldest on Venus, researchers believe that deciphering their early geodynamics could fill in many of the remaining gaps about the evolution of Venus’s surface and atmosphere.

As for the big VERITAS takeaways at the end of the mission?

We’d like to understand why Venus and Earth, once so similar in size and composition, were so different, says Hensley. That has implications for the Rocky planet’s evolution for all discovered exoplanets, he says.

We only have one lab where we can get direct measurements of planets on the surface, and that’s our solar system, says Hensley. So these Venusian observations offer us a key place to test general hypotheses about how rocky planets evolved, he says.