Last Friday we learned about the sun. Now it’s time to learn about the planet closest to the sun, Mercury!
Mercury is the smallest planet in our solar system. It is a bit larger than Earth’s moon. Mercury is 36 million miles away from the sun, or 0.39 AU (remember that one AU, or Astronomical Unit, is 149.60 million kilometers. That’s the distance from the sun to Earth. This unit is used to measure distances throughout our solar system).
It takes Mercury 59 Earth days to rotate once. Consider how long that day would be since it only takes the Earth 24 hours to rotate once. However, because it is so close to the sun, it only take Mercury 88 Earth days to go around the sun. That’s a really short year in Earth time!
During the day, temperatures in Mercury can reach up to 800 degrees Fahrenheit. Although that’s nothing compared to the sun’s photosphere which is 10,000 degrees. At night, Mercury’s temperature can go as low as -290 degrees Fahrenheit. The temperatures are so extreme in part because Mercury really doesn’t have an atmosphere. Instead it has a “thin exosphere made up of atoms blasted off the surface by the solar wind and striking micrometeoroids” (NASA). Sadly these temperature ranges mean that it’s unlikely life (as we know it) could survive on Mercury.
According to NASA, if you stood on the surface at the closet point to the sun, “the sun would appear more than three times larger than it does on Earth.”
Mercury looks very similar to the moon in that it also has craters. These craters were caused by meteoroids and comets hitting the planet. Mercury is the second densest planet in the system (Earth being the densest) and is made up mostly of metallic.
So let’s do a quick recap:
Mercury is the closest planet to the sun. It is also the smallest planet in the solar system. Because it doesn’t have an atmosphere and it’s so close to the sun, it’s temperatures are extremely high and low.