Sunlight not only warms us, it provides energy for photosynthetic plants, which then provide the food and oxygen needed by most other life on our planet.
Light from the Sun takes 8 minutes and 20 seconds to reach Earth. Although this energy reaches Earth quickly, it will have taken millions of years to travel from the Sun’s core to its surface
Astrobiologist Kevin Hand studies icy environments on Earth to understand the potential for life on ice planets and moons.
If you gathered all the water from Juiter’s moon Europa into a ball, it would measure 877 kilometers across. That is more than twice the volume of water on Earth.
Asteroids and comets have delivered water and organic chemicals to Earth since its birth, perhaps aiding the origin of life. But larger impacts can also put an end to life — such as the Chicxulub asteroid that caused the dinosaurs to go extinct 65 million years ago.
Each day, more than 100 tons of material from asteroids and comets falls toward Earth. Most of it is destroyed by friction as it passes through our atmosphere. If one hits the ground it is called a meteorite.
The rovers and spacecraft we’ve sent to Mars have found evidence the planet was warmer in the past, with lakes and rivers. Was there life there? Future exploration may find evidence for that as well.
The gravity on Mars is only 37 percent of Earth’s gravity. Not only could you leap three times higher on Mars, but this lower gravity is one reason why Olympus Mons became the biggest volcano in the solar system.
NASA’s Cassini spacecraft has been orbiting the gas giant planet Saturn and its moons since 2004 and taking stunning images, such as this one of Saturn eclipsing the Sun.
Saturn has 62 moons. One of them, Titan, has a landscape like Earth’s, but the mountains are made of solid ice and the lakes and rivers are methane and haze. Titan is shrouded in a thick chemical smog, so the Cassini spacecraft has to use radar to map its surface.
Although Venus is like Earth in size and mass, it is so hot that the only space probes and landers to visit the surface, the Soviet Union’s Venera missions, melted soon after landing.
The average surface temperature of Venus is 462 °C (864 Fahrenheit). The dense carbon dioxide atmosphere traps heat and causes a greenhouse effect, but in its past Venus might have been more hospitable for life. Venus also has many active volcanoes, another important element for life on our own planet.
NASA’s Kepler Space Telescope has found thousands of planets orbiting distant stars, ranging from gas giants like Jupiter to smaller, rocky worlds more like Earth.
Kepler observes 150,000 stars continuously, looking for very small dips in light. This dip in starlight may indicate that a planet has crossed in front of its host star as it orbits around it.
Our galaxy is shaped like a huge whirlpool, and rotates once every 200 million years. It is so big that light takes 100,000 years to cross from one side to the other.
Not only is our Milky Way galaxy made up of at least 100 billion stars, but scientists estimate there are about 100 billion galaxies in the universe. Scientists think a massive black hole is at the center of most galaxies, including our own.