All objects, including stars and planets, radiate energy to their surroundings. first red-hot and then, as its temperature increases, white-hot like the. But if a planet's various orbital parameters were the only things that each planet then re-radiates that energy as heat back into space. Earth, Mars, and Venus are different distances from the Sun. Venus is the closest and hottest, followed by Earth and then Mars. The heat source for our planet is the sun. Energy from the sun is transferred through space and through the earth's atmosphere to the earth's surface. Geothermal energy originates from the heat retained within the Earth since the original formation of the planet, from radioactive decay of minerals, and from. Venus is the brightest planet in our solar system, has a hellish atmosphere and is covered in volcanoes. Learn more about Venus here. How hot or cold is the surface of a planet? Using some fairly simple physics and math, you can calculate the expected temperature of a planet, including Earth. This Earth energy imbalance (EEI) is the most critical number defining the prospects for continued global warming and climate change. The presence of a significant interior heat source emanating from within hot Jupiter planets appears to be a. Earth's temperature depends on how much sunlight the land, oceans, and atmosphere absorb, and how much heat the planet radiates back to.