In order to further explore our solar system, NASA has chosen four proposals for missions that would investigate Venus, Jupiter's moon Io and Neptune's moon Trident. If chosen, NASA would develop the missions.
The four proposals highlight planets and moons that are not currently included in the agency's ongoing projects. They're part of the agency's Discovery Program, which encourages scientists and engineers to help us explore the solar system by designing new, imaginative mission concepts. Since 1992, the program has supported development for more than 20 scientific instruments and missions.
"These selected missions have the potential to transform our understanding of some of the solar system's most active and complex worlds," said Thomas Zurbuchen, associate administrator of NASA's Science Mission Directorate. "Exploring any one of these celestial bodies will help unlock the secrets of how it, and others like it, came to be in the cosmos."
Two of the proposals involve exploring Venus: One would focus on its atmosphere, while the other would map the planet's surface.
DAVINCI+ stands for Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging Plus. The mission would be dedicated to analyzing Venus' atmosphere to determine how it formed and evolved. It would also investigate the possibility of an ocean in Venus' past.
The mission's instruments, including cameras, would be protected from Venus' harsh environment by a descent sphere.
"The results from DAVINCI+ have the potential to reshape our understanding of terrestrial planet formation in our solar system and beyond," according to a press release from NASA.
VERITAS -- or Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy -- would map the surface of the rocky planet in an effort to shed light on how it turned out so differently from Earth. Our world is often called Venus' twin because the planets are similar in size, but the modern comparisons stop there.
The mission can also provide insight about the geologic history of Venus. The orbiter, equipped with radar, could create 3D topography, allowing scientists to determine how active Venus is volcanically and through plate tectonic processes. It could also study infrared emissions coming off the surface.
Venus likely maintained stable temperatures and hosted liquid water for billions of years before an event triggered drastic changes in the planet, according to a 2019 study. The study author, Michael Way at The Goddard Institute of Space Science, also authored a 2016 study about climate and oceans on Venus in its past.
Now, Venus is a mostly dead planet with a toxic atmosphere 90 times thicker than ours and surface temperatures that reach 864 degrees -- hot enough to melt lead.
The ocean was first suggested by NASA's Pioneer mission in the 1980s. But given its placement as the second planet from the sun, Venus wasn't considered conducive to sustaining an ocean.
Only two NASA missions have visited Venus -- Pioneer in 1978 and Magellan in the early '90s.