In planetary science circles, Venus is now all the rage

Exoplanets continually steal scientific thunder from some of our closest planetary neighbors. But if there is any kind of trend at this year’s Europlanet Society Congress (EPSC), it is the unmistakable wave of resources directed towards future missions to Venus, our infernal planetary companion.

A series of new surface and orbital missions slated for launch by NASA, the European Space Agency (ESA), India and China are creating a new level of excitement for Venus exploration that was not seen since NASA’s Magellan radar mapper visited the planet in 1990 and ESA’s Venus Express began orbiting the planet in 2006.

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

Equipped with tools including radar imaging, radio science and gravity sensing, NASA will launch its VERITAS (Venus Emissivity, Radio Science, InSAR, Topography & Spectroscopy) orbiter mission in November 2027. It is due to arrive on the planet nine months later.

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

The VERITAS spacecraft is first injected into the highly elliptical orbit of approximately 30,000 km and then will perform an aerodynamic braking maneuver for approximately one year. It will then settle into a final scientific orbit of between 180 and 250 km by 2031. Therefore, its nominal two years of full scientific operations will begin only about 2.5 years after launch.

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

NASA notes that three of VERITAS ‘scientific drivers include: What geological processes are currently active on Venus? What are the size and status of the core? And if there is water deep inside Venus, does it reach the atmosphere through volcanism?

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

Because matter?

In general, people don’t want to use the X-band on Venus because so much power is lost in the atmosphere, says Hensley. but we paid for the atmospheric leak by making sure we were able to run the X-band so we could get a very accurate topographic map, she says.

To this end, in terms of resolution, VERITAS will be a little better than Magellan.

There are two types of resolution that might interest you, says Hensley. The most obvious is the spatial resolution; how well are you able to separate things on the surface. The other is radiometric resolution, a measure of how fine the grayscale is on the surface, Hensley says. This gives you more contrast and substance in the data, she says.

To illustrate the difference between Magellan’s radar resolution and what was predicted with VERITAS, Hensley presented a simulation of the big island of Hawaii as seen by Magellan at a resolution of 20 kilometers. It looked a bit like a blurry spot. Veritas, on the other hand, will imagine a spatial resolution of up to 250 meters. That’s two orders of magnitude better than Magellan, says Hensley.

On repeated orbital passes of the planet, VERITAS will be able to combine data from two passes to measure whether the surface has shifted, says Hensley. we’ll be able to determine if a volcano expanding below the surface is causing the ground to swell, she says.

What if Venus was ever habitable?

We want to know if there was water in the past, Hensley says, but determining the timing of the water is much more difficult. However, we hope to be able to determine if water was involved in the formation of continental features on Venus, called tesserae, she says.

Rising steeply two to four kilometers above the planet’s surrounding plains, these highly deformed parts of the surface are believed to be the oldest geological units on the planet. They manifest themselves as circular plateau plateaus with a diameter of up to 2500 km. These so-called “terrains of tiles” dominate the highlands of Venus; covering about 8 percent of the planet’s surface.

Since these terrains are believed to be among the oldest on Venus, the researchers believe that deciphering their early geodynamics could fill many of the remaining gaps on the evolution of both the surface and atmosphere of Venus.

What about the major VERITAS end-of-mission takeaways?

We would like to understand why Venus and the Earth, which were once so similar in size and composition, have evolved to be so different from each other, Hensley says. This has implications for the evolution of the planet Rocky for all exoplanets discovered, she says.

We only have one laboratory where we can get direct measurements of the planets on the surface and this is our solar system, says Hensley. Hence, these observations of Venus provide us with a key place to generically test hypotheses about how rocky planets evolved, she says.


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