Free Astronomy Magazine July-August 2021

11 JULY-AUGUST 2021 ASTRO PUBLISHING A n artist's concept of active vol- canos on Venus, depicting a sub- duction zone where the foreground crust plunges into the planet's inte- rior at the topographic trench. [NASA/JPL-Caltech/Peter Rubin] phere and surface give us a solid foundation to begin to rewind the history of Venus to consider, just as has been done so effectively for Mars, if its ancient surface was more hospitable than today. Extrasolar planets − This magazine has often discussed habitability and, even more recently, technosigna- tures – for which the focus on rocky planets within Goldilocks Zones still very much seems to be the center of discussions within the larger com- munity. This makes the paradox of the Venus-Earth-Mars triplet so in- teresting – Mars is barely habitable, but at least, in terms of surface con- ditions, its best days are not too dis- similar from what some on Earth would consider extremely uncom- fortable. That said, visitors from Earth could at least complain about the temperature (and radiation if their suits were properly equipped) with a far less cumbersome body suit than worn by astronauts per- forming maintenance on the ISS. Earth is, of course, Earth, providing a wide range of environmental con- ditions but no surface extreme so great that some form of life cannot be found or even thriving. Venus is the oddity in this series – we would expect higher surface temperatures and harsher environ- mental conditions in general, simply by its proximity to the Sun. That said, the Venusian environment is severe beyond our current ability to explain why it is so. Models of vol- canism, catastrophic collisions, and even ocean evaporation are re- ported in the literature to explain how such a massive amount of at- mospheric CO 2 could have been re- leased over time to foster the planet’s runaway greenhouse ef- fect. The greater abundance of cer- tain isotopes of the Noble elements are also indicators of certain atmos- pheric and geochemical phenom- ena that are potential explanations for the current conditions on Venus. It may be discovered among solar systems similar in number and plan- etary placements to ours that all rocky planets near the Sun undergo the same kinds of evolution that our system has. Alternatively, we may discover that the reason for the brutal conditions of Venus are unique to its own evolution and similarly-placed planets in other solar systems are more hospitable, making them more suitable to sup- porting the development of living organisms. If all development goes as planned, both missions are set to be launched between 2028 and 2030. They will be soon followed by a very recently announced European Space Agency (ESA) mission named EnVision, set for launch in the early 2030s. !