Extrasolar planets continually steal scientific thunder from some of our closest planetary neighbors. But if there’s any sort of trend at this year’s Europlanet Society Congress (EPSC), it’s the undeniable 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 has not not been 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 drivers for all this activity. The first is that we must understand our netherworld neighbor with extraordinarily high surface temperatures and pressures, if we are ever to understand extrasolar planetary systems like 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 own long-term atmospheric models.
Equipped with instruments including radar imaging, radioscience and gravity sensing, NASA will launch its VERITAS (Venus Emissivity, Radio Science, InSAR, Topography & Spectroscopy) orbital mission in November 2027. It is expected to arrive at planet nine months later.
Scientists will use VERITAS data to create the world’s first high-resolution maps of radar imagery and topography, according to NASA. Surprisingly, planetary scientists still use Magellan data. But veritas will take Venus surface radar imagery to the next level.
The VERITAS spacecraft is first injected into the very elliptical orbit of approximately 30,000 km and then performs an aerobraking maneuver for approximately one year. It will then settle into a final science orbit of between 180 and 250 km by 2031. Thus, its nominal two years of full science operations will not begin until 2.5 years after launch.
VERITAS will produce the first maps of surface rock composition and limit surface weathering by observing the planet’s dense atmosphere through infrared spectral windows, according to NASA. The mission will also search for thermal and chemical signatures of recent and active volcanism.
NASA notes that three of VERITAS’ science engines include: What geological processes are currently active on Venus? What is the size and condition of the core? And if there is water deep inside Venus, does it reach the atmosphere via volcanism?
In order to maximize its surface mapping of Venus’ topography with very high accuracy, 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, radar scientist at NASA’s Jet Propulsion Laboratory and mission project scientist, told me here in Grenada. VERITAS. Magellan’s S-band radar had a wavelength of about 12 centimeters, he says. We’re in X-band, so we have a wavelength of about four centimeters, Hensley explains.
Why is this important?
Generally speaking, people don’t want to use X-band at Venus because you lose so much power in the atmosphere, Hensley says. but we paid for the atmospheric loss by making sure we could use X-band to get a very accurate topographic map, he says.
To that end, in terms of resolution, VERITAS will be a bit better than Magellan.
There are two types of resolution you might be interested in, says Hensley. The most obvious is the spatial resolution; how good you are at separating things on the surface. The other is radiometric resolution, a measure of the fineness of the grayscale at the surface, Hensley explains. This gives you more contrast and substance in the data, he says.
To illustrate the difference between Magellan’s radar resolution and what is predicted with VERITAS, Hensley presented a simulation of the Big Island of Hawaii as seen by Magellan at 20 kilometer resolution. It looked a bit like a blurry blob. Veritas, on the other hand, will produce images up to a spatial resolution of 250 meters. That’s two orders of magnitude better than Magellan, says Hensley.
During repeated orbital passes of the planet, VERITAS will be able to combine data from two passes to measure whether the surface has moved, Hensley says. we will be able to determine if an expanding volcano below the surface is causing the terrain to bulge, he says.
As to whether Venus was ever habitable?
We want to know if there was water in the past, says Hensley, but determining when the water was is much more difficult. However, 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 steeply about two to four kilometers above the surrounding plains of the planet, these highly deformed parts of the surface are considered the oldest geological units on the planet. They manifest as circular highland plateaus that extend up to 2500 km in diameter. These so-called “Testerae Lands” dominate the high plateaus of Venus; covering about 8% of the planet’s surface.
Because these terrains are considered to be among the oldest on Venus, the researchers believe that deciphering their early geodynamics could fill in many of the remaining gaps regarding the evolution of Venus’ surface and atmosphere.
As for the main takeaways from VERITAS at the end of the mission?
We’d like to understand why Venus and 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 Planet Rocky for all exoplanets discovered, 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 Venus observations provide us with a key place to generically test hypotheses about the evolution of rocky planets, he says.
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