Jupiter doesn't stop other planets from being hit by asteroids. It's actually raises the stakes. Jupiter takes cosmic debris into it's orbit and sometimes launches it at other planets. (including Earth!) Although in some cases Jupiter takes the cosmic debris/asteroids and launches them away from the planets. It's kinda like a cosmic game of dodgeball, lol.
Asteroids, by definition, are much smaller than planets. That's one reason why they are mostly shaped irregular, unlike planets which are close to being round. The round shape is due to the increased mass (or weight) and only large masses tend to be round due to gravity.
For an object to be a planet it has to : orbit the sun, has enough mass to assume a rounded shape, and clear any objects in its path. Some planets (such as Pluto) are no longer planets because they do not fit the criteria above. They are then usually classed as dwarf planets. Asteroids are small pieces of rock which orbit the sun. These are much too small to become planets/dwarf planets and also don't fit the criteria above. Hope this helps :)
Objects that orbit a planet are called moons or satellites, they are not planets. Both Mars and Jupiter have moons; Jupiter has a lot more than Mars does, and some of them are quite large, too. The two moons of Mars, Phobos and Deimos, are relatively small, perhaps even tiny.
An infinite number of planets have more than one moon. Of the planets in our solar system, 3 (Mars, Saturn, and Jupiter), have more than one moon. Mars has two moons, Jupiter has at least 63, and Saturn has 60 not counting the asteroids that make up its rings.
They are not protected from collisions. What helps is that the average distance between asteroids is immense, such that one asteroid is not likely visible to the naked eye to the next nearest asteroid. There is so much space between asteroids the ships generally pass through without any problem. Actually, the rings of Saturn are also so tenuous that the Cassini spacecraft has passed through them with no ill effect, and they are MUCH denser than the asteroid belt.
Jupiter's strong gravity deflects or captures many asteroids that could otherwise collide with the inner planets. Its massive size also acts as a gravitational shield, pulling in or disrupting incoming debris from the outer solar system. This phenomenon is known as the "Jupiter shield" or "Jupiter's protection."
In between the planets Mars and Jupiter is a feature called the Asteroid Belt, which is a large area of asteroids, or space rocks. Some of these asteroids are hundreds of miles in diameter, and some are just boulder-sized. Some have regular orbits like the planets, others have orbits that are highly eccentric and actually cross the orbits of other planets like Earth, which means that collisions are possible. Dozens of these asteroids have actually been captured by the planets Jupiter and Saturn and are now natural satellites of those planets. Other asteroids are gravitationally "nudged" by planets occassionally during their trek around the sun. There are several theories about their existence, including them being the remnant of a failed planet that tried to form during the earliest part of our Solar System's history. Asteroids have been portrayed inaccurately in media; if you could travel through the Asteroid Belt, you would likely never even see one. Despite the large number of asteroids, the space they occupy is vast, and they are widely scattered.
Because of its mass, Jupiter has likely collided with more asteroids, planetesimals, comets and other small bodies than any other planet in the Solar system. The asteroid belt only gets as close to Jupiter as it does because Jupiter has perturbed the orbits of all asteroids that were closer to Jupiter, either impacting directly, locking them into orbit of Jupiter to become a moon, or causing the asteroids to slingshot away. Many millions of years in the past, there were a lot more asteroids, and they were not confined to the asteroid belt, but the gravitational pull of Jupiter and the other planets have "swept" most of the solar system of these small bodies.
The Asteroid Belt orbits between Mars and Jupiter, at about 3 AU. There are several objects not properly classified as asteroids orbiting within the belt, mainly the dwarf planet Ceres and the protoplanets Vesta and Pallas.
Asteroids, by definition, are much smaller than planets. That's one reason why they are mostly shaped irregular, unlike planets which are close to being round. The round shape is due to the increased mass (or weight) and only large masses tend to be round due to gravity.
The small planets that orbit between Mars and Jupiter are primarily known as the asteroids, which make up the asteroid belt. This region contains a vast number of rocky bodies, with Ceres being the largest and classified as a dwarf planet. Other notable asteroids include Vesta, Pallas, and Hygiea, among many others. These celestial objects vary in size and composition, providing insights into the early solar system.
Like all orbiting bodies, an asteroid moves in an ellipse. Compared to the planets, these orbits have a higher probability of being more eccentric ("stretched out", further from being a circle). That is why some asteroids cross the orbit of the earth. Most asteroids move in near-circular orbits between Mars and Jupiter. A close approach to another asteroid or one of these planets can alter the orbit to a more eccentric one.
The Sun is a star at the center of the solar system, providing heat and light to the planets. The eight planets vary in size, composition, and distance from the Sun, with Mercury being the smallest planet closest to the Sun and Neptune being the farthest gas giant. Moons orbit many of the planets, with some having more than others. For example, Jupiter has the most moons in the solar system. Asteroids and comets also exist in the solar system, with asteroids being rocky and comets being icy.
For an object to be a planet it has to : orbit the sun, has enough mass to assume a rounded shape, and clear any objects in its path. Some planets (such as Pluto) are no longer planets because they do not fit the criteria above. They are then usually classed as dwarf planets. Asteroids are small pieces of rock which orbit the sun. These are much too small to become planets/dwarf planets and also don't fit the criteria above. Hope this helps :)
Objects that orbit a planet are called moons or satellites, they are not planets. Both Mars and Jupiter have moons; Jupiter has a lot more than Mars does, and some of them are quite large, too. The two moons of Mars, Phobos and Deimos, are relatively small, perhaps even tiny.
An infinite number of planets have more than one moon. Of the planets in our solar system, 3 (Mars, Saturn, and Jupiter), have more than one moon. Mars has two moons, Jupiter has at least 63, and Saturn has 60 not counting the asteroids that make up its rings.
They are not protected from collisions. What helps is that the average distance between asteroids is immense, such that one asteroid is not likely visible to the naked eye to the next nearest asteroid. There is so much space between asteroids the ships generally pass through without any problem. Actually, the rings of Saturn are also so tenuous that the Cassini spacecraft has passed through them with no ill effect, and they are MUCH denser than the asteroid belt.