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Contrary to popular imagery, the asteroid belt is mostly empty. The asteroids are spread over such a large volume that reaching an asteroid without aiming carefully would be improbable. Nonetheless, hundreds of thousands of asteroids are currently known, and the total number ranges in the millions or more, depending on the lower size cutoff.
Terrestrial planets are substantially different from the giant planets, which might not have solid surfaces and are composed mostly of some combination of hydrogen, helium, and water existing in various physical states. Terrestrial planets have a compact, rocky surfaces, and Venus, Earth, and Mars each also has an atmosphere. Their size, radius ...
Most chondrules are composed primarily of the silicate minerals olivine and pyroxene, surrounded by feldspathic material that may either be glassy or crystalline. Small amounts of other minerals are often present, including Fe sulfide ( troilite ), metallic Fe-Ni, oxides such as chromite , and phosphates such as merrillite .
The layers of the Earth, a differentiated planetary body. In planetary science, planetary differentiation is the process by which the chemical elements of a planetary body accumulate in different areas of that body, due to their physical or chemical behavior (e.g. density and chemical affinities).
The origin of water on Earth has long been a contested question — water forms in the course of many chemical reactions, and it is also a major component of comets. A new study reveals that ...
These are composed primarily of S-type asteroids, whereas the neighboring Hungaria family includes some E-types. [101] The Phocaea family orbit between 2.25 and 2.5 AU from the Sun. [102] Skirting the outer edge of the asteroid belt is the Cybele group, orbiting between 3.3 and 3.5 AU. These have a 7:4 orbital resonance with Jupiter.
In this dramatic illustration, a meteor falls toward Earth from space. A pair of asteroids that rammed into Earth more than 35 million years ago seemingly had no climate impacts, scientists said ...
The NASA spacecraft OSIRIS-APEX hovers over the surface of the near-Earth asteroid Apophis, using its thrusters to disturb the asteroid's surface to reveal what lies beneath, as shown in an ...