Jupiter is a lot bigger, so it looks brighter even though it is further away. Mars can be quite bright for a few weeks around the time of opposition, which happens every 780 days or just over two years, the next time 22-05-2016.
Mercury, Venus, Mars, Jupiter, and Saturn can easily be seen with the naked eye. Visibility changes from year to year; you may want to look up information about specific planets, for specific months and years. For example, at the time of this writing (Oct. 2009), Jupiter can be seen after sunset, as a spectacularly bright star, high in the sky. It will set a few hours later.
From Mars, Jupiter appears as a bright point of light in the sky. It is much larger and brighter than any other star visible from Mars. Jupiter's distinct orange and white bands may also be visible with a telescope.
Up! ; ) Jupiter is far brighter than any star. It's in the east on October evenings. Grab a pair of binoculars and you may even get to glimpse its' moons also.
The five planets visible from Earth without a telescope are Mercury, Venus, Mars, Jupiter, and Saturn. These planets are often visible to the naked eye and can be seen in the night sky from various locations on Earth at different times throughout the year.
Like the moon, all the planets get their apparent brightness by reflecting light towards us from the Sun. At some stages Mars is reflecting more light towards Earth, so it appears to be brighter. Also, sometimes it is closer than at other times, so it appears to reflect more light towards us.
It's best to look at them through a telescope at night.
This is a function of distance - an object appears smaller the further away it is. Although Jupiter is many times the size of Mars, the two planets appear to be about the same size because Jupiter is also much further away from Earth than Mars is.
Hardly right now (June 2013), since it is almost exactly in the direction of the Sun. However, when it is in another direction, it is the second-brightest "star" (planets look like stars), after Venus, which is also a planet; you might also say that Jupiter is the fourth-brightest object in the sky, after Sun, Moon, and Venus. (On rare occasions, Mars is slightly brighter than Jupiter.)
Hardly right now (June 2013), since it is almost exactly in the direction of the Sun. However, when it is in another direction, it is the second-brightest "star" (planets look like stars), after Venus, which is also a planet; you might also say that Jupiter is the fourth-brightest object in the sky, after Sun, Moon, and Venus. (On rare occasions, Mars is slightly brighter than Jupiter.)
Mercury, Venus, Mars, Jupiter, and Saturn are easily visible in the sky without a telescope or binoculars, if you know when and where to look. That information is often included on the weather page of the local newspaper.
They are different sizes and distances from us, and so they reflect different amounts of light.
They look like points of light. On first sight, a planet might be confused with a star (a very bright star, in the case of Venus, Jupiter, and sometimes Mars). Planets shine brightly and do not flicker while stars do not shine as bright (usually) and they always flicker, or sparkle.
Look up in the sky and you will see. Polaris is actually quite dim, compared to other stars and planets. Even at it's dimmest, Mars is brighter than Polaris.
Mercury, Venus, Mars, Jupiter, and Saturn can easily be seen with the naked eye. Visibility changes from year to year; you may want to look up information about specific planets, for specific months and years. For example, at the time of this writing (Oct. 2009), Jupiter can be seen after sunset, as a spectacularly bright star, high in the sky. It will set a few hours later.
What do you mean by "biggest"? That it looks brightest? That its real brightness is the greatest? That it has the largest diameter? The greatest mass? The star that looks brightest for us is Sirius. Planets, however, also look like stars, and some of them look brighter than Sirius, including Venus, Jupiter, and sometimes Mars.
From Mars, Jupiter appears as a bright point of light in the sky. It is much larger and brighter than any other star visible from Mars. Jupiter's distinct orange and white bands may also be visible with a telescope.
Up! ; ) Jupiter is far brighter than any star. It's in the east on October evenings. Grab a pair of binoculars and you may even get to glimpse its' moons also.