Mercury is the closest planet to the sun and the smallest one in our solar system. It’s so tiny that it’s even smaller than some moons that orbit other planets! People have been observing Mercury for over 2,000 years, but there’s still a lot we don’t know about it.
Because Mercury is so close to the sun, about 36 million miles away, it’s hard to see from Earth. The best time to spot Mercury is during twilight, either at sunrise or sunset. When you do see it, Mercury shines brightly in the sky.
Mercury is named after the Roman messenger of the gods, who was known for his speed. Just like its namesake, Mercury is super fast! It zooms around the sun in just 88 days, which is the shortest orbit of any planet. But it spins slowly; while Earth takes 24 hours to rotate once, Mercury takes 59 days!
Even though Mercury is closest to the sun, it’s not the hottest planet. That’s because it has almost no atmosphere to trap heat. During the day, temperatures can get extremely hot, but at night, they drop way below freezing.
Mercury is one of the four rocky planets in our solar system, just like Earth. Its surface is solid and covered in craters, making it look a lot like our moon. Interestingly, Mercury doesn’t have any moons or rings.
Two important spacecraft have visited Mercury. The first was Mariner 10 in 1975, which took the first close-up pictures of Mercury’s surface and mapped about 45% of it. Then, the MESSENGER mission started in 2011 and orbited Mercury, helping to map most of the rest of the planet.
MESSENGER made an exciting discovery: it found evidence that Mercury once had active volcanoes! Pictures showed shield volcanoes and old lava flows, suggesting that Mercury was more active in the past than we thought.
Scientists are still studying Mercury to learn more about this small and mysterious planet. As they continue their research, we hope to discover more about its history and what makes it unique. Mercury is a fascinating part of our solar system, and there’s still so much to explore!
Mercury Observation Journal: Try to spot Mercury in the sky during twilight, either at sunrise or sunset. Keep a journal of your observations. Note the date, time, and what the sky looked like. Draw a picture of what you see. How does Mercury’s brightness compare to other stars or planets you can see?
Speedy Mercury Race: Create a fun game to understand Mercury’s fast orbit. Use a hula hoop or draw a large circle on the ground to represent the sun. Have one child be Mercury and another be Earth. Mercury should run around the circle 4 times while Earth runs around once. Discuss how Mercury’s orbit is much faster than Earth’s.
Temperature Experiment: Explore temperature extremes like those on Mercury. Place a thermometer in a sunny spot and another in a shaded area outside. Check the temperatures after an hour. Discuss how Mercury’s lack of atmosphere causes big temperature changes, similar to the difference between the sunny and shaded areas.
