Which planet is less than half the diameter of the earth and look like your own moon?

Answer 1

Mercury best answers this question, as it is the only planet less than half the size of Earth (whereas Mars is about 2/3rds the size of Earth and Venus about 3/4ths) and has almost no atmosphere (like the moon) (whereas Mars has much more atmosphere than the Moon or Mercury, though quite thin compared with the other planets, and Venus has a very thick atmosphere even compared with Earth); this lack of atmosphere lets craters accumulate on Mercury's surface, much like our Moon's; on Venus, Earth and Mars, our atmospheres are thick enough that fewer asteroids are able to survive descent to create craters in the first place and even when asteroids and other bodies in space are able to impact the surfaces of Venus, Earth or Mars, weather will, over time, erode away those impact craters (even on Mars; its atmosphere is sufficiently thick to give it very impressive dust storms which can erode raised crater rims and fill crater basins).

However, Mercury has a number of significant differences than the moon, chiefly that it is much denser (in fact, it is denser than earth and all other planets) with a large iron core (the moon has very little iron by comparison) ... in fact, Mercury's iron core is estimated to be larger than Earth's (but has much less stuff outside the core, so the planet overall is significantly smaller than Earth). The moon has no magnetic field of its own, but Mercury does (although only about 1% as strong as earth's). Because it is much closer to the sun, Mercury is much warmer than our Moon.