Oct 21, 2025 · NASA’s real-time science encyclopedia of deep space exploration. Our scientists and far-ranging robots explore the wild frontiers of our solar system.

Stray asteroids and asteroid fragments have slammed into Earth and the other planets in the past, playing a major role in altering the geological history of the planets and in the evolution of life …

Of the terrestrial (rocky) planets of the inner solar system, neither Mercury nor Venus have any moons at all, Earth has one and Mars has its two small moons. In the outer solar system, the …

The Sun orbits the center of the Milky Way, bringing with it the planets, asteroids, comets, and other objects in our solar system. Our solar system is moving with an average velocity of …

According to one well-supported theory, the shifting orbits of the four giant planets (Jupiter, Saturn, Uranus, and Neptune) could have caused most of the original material -- likely 7 to 10 …

Oct 21, 2025 · Mars is the fourth planet from the Sun, and the seventh largest. It’s the only planet we know of inhabited entirely by robots.

Over time, the orbits of most large satellites or planets tend to become circular, but that isn't the case for these three. Their resonance forces their orbits to become slightly elliptical, or eccentric.

Asteroids and comets – and the meteors that sometimes come from them – are leftovers from the formation of our solar system 4.6 billion years ago.

Each planet in the inner solar system is less dense than its inner neighbor – Mars is less dense than Earth, which is less dense than Venus, which is less dense than Mercury.

Oct 21, 2025 · Pluto was once our solar system's ninth planet, but has been reclassified as a dwarf planet. It's located in the Kuiper Belt.