Why is Venus hotter than Mercury, when Mercury is closer to the Sun?

The surface of Venus, as reconstructed from radar data collected by NASA's Magellan mission. NASA/JPL, CC BY-NC-SA Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to CuriousKidsUS@theconversation.com. Why is Venus the hottest planet, whereas Mercury is closer to the Sun? – Sejal M., age 7, Bangalore, India When the solar system had just formed, 4.5 billion years ago, Venus was probably a tropical paradise. Oceans of water likely…