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Gaspra Asteroid

 #951  19 x 12 x 11 km

Mathilde Asteroid

#253  66 x48 x 46 km (33 miles)


Mathilde, Gaspra, Ida Asteroids Size Comparison

Toutatis Asteroid

#4179  4.6 x 2.4  x 1.9 km


Asteroids have many mysteries surrounding them.  Asteroids are defined as minor planets.  Most of our solar system's asteroids are found between Mars and Jupiter, in an enormous ring (or belt) encircling the sun.  Other asteroids are found circling around planets.  We call these moons or natural satellites.   And finally, some asteroids have asteroids circling around them.  These are also called satellites.  Our largest asteroid is Jupiter's moon Ganymede at 3,275 miles.  Our largest asteroid, that's not a moon, is about 2320 km (1441 miles) in diameter and has a moon 1270 km in diameter.  This asteroid is on the outer edge of our solar system and we call it Pluto.  In the inner circle, between Mars and Jupiter, the largest and first asteroids discovered was 'Ceres' with a 960 km (485 miles) diameter.  Asteroids traditionally have very circular orbits, unlike comet orbits which are very oval.

Amazingly, 10 tons of meteorites hit the Earth's atmosphere every day.  Most are only the size of a grain of sand.  (Good thing, huh?)   Meteorites are not asteroids (generally they are smaller), although, both can cause impact craters when they crash into other larger asteroids or planets.  Normally, these mini asteroids that fall towards Earth burn up when they pass through our atmosphere.  These are what we see as 'falling stars'.  There are an estimated 30,000 recognizable asteroids in the belt, 6000 currently have names, and by the end of this year we should have close to 10,000 named. (Go technology)!  In fact, we have a satellite, NEAR, which will take pictures of Eros Asteroid, this February.  Most asteroids are thought to consist of heavy Iron materials; but, Mathilde (below) was concentrated carbon, more than a piece of charcoal, and could be the darkest object in our system.


Ida, #243, measuring 58 x 23 x 25 km with its moon (the dot on the right). 

Ida's moon name is Dactyl. Ida's moon 1.2 x 1.4 x 1.6 km.  Some craters are1000 feet.



(Left) The crater in the middle is 10+ miles across. (Above) Mathilde's largest crater is 19 miles across.

Asteroid Information

*Amors, Apollos, and Atens are the three categories of Near-Earth asteroids (NEAs). Amor asteroids approach the Earth's orbit from the outside, Apollo asteroids cross the Earth's orbit, and Aten asteroids approach the Earth's orbit from the inside. Potentially Hazardous asteroids (PHAs) are larger than ~200 m (0.1 mile) and approach close enough to present a potential hazard but not a current hazard.



Date Discovered

Size (KM/Mi)


2002 MB RR0067C


16 June

3 (1.8)


2002 MT1 RSRP8HB


21 June

0.3 (0.2)



On June 16th, 2002 a nearly 2 mile wide asteroid was discovered on an oval orbit located within the inner planets. Its orbit does not immediately affect Earth’s. But playing with the orbit trackers and it seems that it will come incredibly close, or perhaps…, to Venus.

An asteroid that they are talking about is June 21st. It is .2 of a mile wide. It only needs to be .1 of a mile to do serious damage.  It ran along side us for about a month and  continued to get closer as our orbit curved outward. If you took the distance that the Earth is from the sun, the asteroid came about .1 that distance.  It passed us July 20th, 2002 or so…

There are pictures and graphics with animation attached at NASA. And, in case anyone is interested the NASA web site is  . If you visit the site it is just a bunch of numbers, but just click on the orbit buttons in the graphs and you can see all the pictures…