Exoplanets are constantly stealing science thunder from some of the planets closest to us. But if there is any kind of trend at this year’s European Planetary Society Conference (EPSC) it is an unmistakable wave of resources geared toward future missions to Venus, our infernal planetary companion.
A series of new surface and orbital missions scheduled for launch by NASA, the European Space Agency (ESA), India and China are creating a new level of excitement about Venus exploration not seen since NASA’s Magellan radar chart visited the planet. In 1990, the European Space Agency’s Venus Express began orbiting the planet in 2006.
There are two main drivers of all this activity. The first is that we need to understand our infernal neighbors with unusually high temperatures and surface pressures, if we are to understand exoplanet systems like ours. And second, a better understanding of the harms of climate change here on Earth. We need to understand what went wrong on Venus in order to help improve our long-range atmospheric models.
Equipped with instruments including radar imaging, radio science and gravity sensing, NASA will launch its orbital mission VERITAS (Venus Emissivity, Radio Science, InSAR, Topography & Spectroscopy) in November 2027. It is scheduled to reach the planet nine months later.
Scientists will use VERITAS data to make the world’s first high-resolution radar and terrain maps, according to NASA. Surprisingly, planetary scientists still use Magellan’s data. But Veritas will take radar imaging of the surface of Venus to the next level.
The VERITAS spacecraft is first injected into a highly elliptical orbit of about 30,000 km, and then does the air braking maneuver for about a year. It will then settle into a final scientific orbit of 180-250 km by 2031. Thus, two years of full scientific operations will begin just 2.5 years after its launch.
Veritas will produce the first maps of surface rock formation and surface weathering restriction by gazing through the planet’s dense atmosphere through infrared spectral windows, NASA says. The mission will also search for thermal and chemical signatures of both recent and active volcanoes.
NASA notes that three of VERITAS’ science drives include: What geological processes are currently active on Venus? What is the size and state of the kernel? And if there is water deep in the interior of Venus, does it reach the atmosphere by volcanoes?
In order to maximize surface mapping of Venus’ topography at very high resolution, Veritas will use a different radar wavelength than Magellan’s. 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 Veritas mission scientist, told me here in Granada. The wavelength of the Magellan S-band radar is about 12 cm. We’re an X band, Hensley says, so we have a wavelength of about four centimeters.
Why is this important?
In general, people don’t want to use the X-band on Venus because you lose a lot of strength in the atmosphere, says Hensley. But we paid for the atmospheric loss by making sure we were able to do the X-band so we could get a very accurate topographic map, he says.
To that end, in terms of accuracy, VERITAS will be slightly better than Magellan.
There are two types of decision you might be interested in, says Hensley. The obvious is the spatial resolution. How well you can separate objects on the surface. The other is radiative resolution, which is a measure of how fine the grayscale is on a surface, says Hensley. This, he adds, gives you more contrast and substance in the data.
To illustrate the difference between the accuracy of Magellan’s radar and what is expected with Veritas, Hensley provided a simulation of the Big Island of Hawaii as if Magellan saw it with an accuracy of 20 kilometers. It seemed like a vague point. By contrast, Veritas will shoot with a resolution of up to 250 metres. This is two orders of magnitude better, says Hensley, than Magellan.
In the planet’s frequent orbital passes, Veritas will be able to collect data from two trajectories to measure whether the surface has moved, Hensley says. We will be able to determine if a volcano expanding below the surface is causing the terrain to bulge, he says.
As for whether Venus is habitable at all?
We want to know if there was water in the past, says Hensley, but determining when to water is more difficult. However, we hope we will be able to determine if water is involved in forming continent-like features on Venus, called a trough, he says.
These highly deformed parts of the surface, which rise about 2 to 4 kilometers above the plains surrounding the planet, are believed to be the oldest geological units on the planet. They appear as circular plateaus in the highlands, with a diameter of up to 2500 km. This so-called “facilitation” terrain dominates the high plateaus of Venus; Covering about 8% of the planet’s surface.
Because this terrain is thought to be among the oldest on Venus, the researchers believe that deciphering their early geodynamics could fill in many of the remaining gaps about Venus’ surface and atmospheric evolution.
As for the main fast food Veritas at the end of the job?
We’d like to understand why Venus and Earth, which were so similar in size and composition, evolved to be so different from one another, says Hensley. He adds that this has implications for the evolution of rocky planets for all exoplanets discovered.
“We only have one laboratory where we can get direct measurements of planets on the surface, and that is our solar system,” says Hensley. Therefore, these Venus observations provide us with a prime place to test hypotheses in general about how rocky planets evolved, he says.