A lot of people consider meteorites harmful to our planet. However, it’s no big deal. Earth is hit by space rocks every day but rarely notices them.
First, how to distinguish different kinds of space rocks?
It turns out to be very easy if you get all the parameters and the definitions of the asteroids. So, here are some types of space rocks you can learn.
- Comets
- Asteroids
- Meteoroids / Meteorites / Meteors
- NEOs
- Kuiper Belt Objects
- Oort Cloud Objects
Did you get that? If not, don’t worry because we’ll explain them one by one. Comets are dubbed “dirty snowballs’ due to the icy, rocky and dusty composition of them. Comets are pretty tiny relative to our planet, as small as asteroids. But, they have significantly elliptical orbit because its perihelion and aphelion are very distinct.
Asteroids, as we all know, are irregular and tiny rocks that float in space. Most asteroids are from the Asteroid Belt between Jupiter and Mars, but sometimes they fly really close to Earth. These asteroids are known as NEOs. To read more, visit https://cneos.jpl.nasa.gov/.
Others are either comets or asteroids, only depending on their location. Understand? Kuiper Belt objects are from the Kuiper Belt, and Oort Cloud objects are from the Oort Cloud.
When an asteroid arrives at Earth, it becomes either a meteorite, meteoroid, or a meteor. So, how to differentiate between the three? A meteoroid has not entered the atmosphere yet, but meteors did. If the meteor is too small, it burns up before reaching the ground. But, if it does impact Earth, we call them a meteorite.
So, how many space rocks hit Earth every day?
Firstly, we need to talk about their quantities, as most people think about that first when reading the title. Near Earth Objects are unbelievably numerous. They can range in the trillions. But, all objects, including space junk, counts, right? Surprisingly, our planet is hit by 100 tons of space rock every day, enough to fill a Boeing 747 thoroughly!
But why do tons of space rocks still exists after billions of years of evolution? Well, it turns out that it could be new, born in a collision of multiple space rocks. It can also be leftovers from the formation. After all, the amount of rocks and dusts born with the Solar System is uncountable, so there are undoubtedly some that are fortunate not to collide with any planet before.
More about Near Earth Objects
NEOs, or as Near Earth Objects, are Minor Planets that are close to Earth, and must be closely monitored. If they are large and cross its orbit with Earth, it is considered a PHA (Potentially Hazardous Asteroid). There are 7 types of NEOs, with one being PHAs.
They are in 2 major categories: NECs and NEAs. Near Earth Comets are short-period comets whose perihelion is less than 1.3 AU, whilst Near Earth Asteroids are ones who fit the same perihelion criteria. Atiras are NEOs entirely inside Earth’s orbit, and Amors are fully outside Earth’s orbit, both posing a zero threat. But, if they turn into one of these, we can have a chance to collide with it.
Atens, Apollos, and PHAs have possibilities to be destroyed by a collision to Earth because they cross Earth’s orbit. Atens are mostly inside Earth’s orbit, while Apollos are likely to be outside Earth’s orbit at a given moment. If an Aten or Apollo asteroid is huge and has a near MOID (Minimum Orbit Intersection Distance) with Earth, it is a PHA. They have a much better chance of colliding Earth with destructions, so they must be urgently monitored.
To sum up, although PHAs are harmful, it’s always better to have them since they are once the building blocks of our planet. Without these asteroids, Earth wouldn’t exist, let alone thriving with life.
Credits
- “NASA – Space Rocks”, NASA, https://www.nasa.gov/audience/forstudents/5-8/features/F_Space_Rocks.html
- “NEO Basics”, Center for NEO Studies, https://cneos.jpl.nasa.gov/about/neo_groups.html
- Phoenix7777, “2020 QG”, Wikipedia, HORIZONS, JPL, NASA, https://en.wikipedia.org/wiki/2020_QG#/media/File:Animation_of_2020_QG_orbit_around_Earth.gif
- “School Bus-Size Asteroid to Safely Zoom Past Earth”, NASA, https://www.nasa.gov/sites/default/files/thumbnails/image/asteroid20200922-16.jpg