Venus is the second planet from the Sun, and the most like Earth in terms of its mass (80% Earth’s) and size (95% Earth’s). In almost every other aspect it is radically different. It has a thick, carbon dioxide atmosphere, little water, a weak magnetic field, and a surface temperature of 740 K (860 F, 460 C). Despite this radical difference, early Venus was a wet world much like early Earth. We know from the levels of hydrogen and deuterium in Venus’ atmosphere that it too had a wet past. But somehow Venus and Earth diverged.
Alas, Poor Ceres
In 1801 a new planet was discovered in our solar system. Just twenty years earlier the planet Uranus was discovered beyond the orbit of Saturn, and was the first planet discovered since the dawn of civilization. This new planet was named after the Roman goddess of agriculture, Ceres.
Icy Hot
Mercury is the closest planet to the Sun. You might think that means it is also the hottest planet, but that award goes to Venus with its thick, heat-trapping atmosphere. Mercury can be listed as one of the hottest planets in the solar system, but also one of the coldest.
The Great Migration
We know that the planets in our solar system migrated from their points of formation to their current positions. Just how that occurred is a bit of a mystery.
Water on Ceres
Water vapor has been discovered on Ceres. It is the first confirmation of water on a member of the asteroid belt.
Border Crossing
Eventually, the stream of the solar wind slows down enough that the interstellar wind can push back, which creates a boundary known as the heliopause. Beyond the heliopause, the interstellar wind dominates. Beyond the heliopause is interstellar space.
Close Encounters
Just how stable is the solar system against close encounters with stray planets? Pretty stable, and we can show that with a bit of computational physics.