Right now in June, 2009, Mars is easily visible in the eastern sky starting about 2 hours before dawn. As the Earth catches up with Mars in its orbit, it will rise earlier and earlier, until early next year it will be easily visible in the evening sky as well.
Mars can be seen from the Earth without a telescope, people have known about its existence since the stone age.
Mars Year: once.Earth Year: 0.53 times.
one year round trip
Mars. The further out from the sun, the longer a planet takes to revolve round the sun. For example, Pluto's orbit takes over 200 (Earth) years.
Humans first found out about Mars by looking up at the night sky. At some times of the year, it is visible like Venus- you just need to know where to look. The telescope helped a lot to understand more.
Hubble has never "explored" Neptune. It is a telescope in orbit round Earth and from Earth it has "imaged" Neptune. It has done this several times eg 1996 and 1998 (there may be more times!).
Actually, with a knowledge of where to look (check any almanac) and good seeing conditions, you can spot five of the other seven planets with the naked eye: Mercury, Venus, Mars, Jupiter, and Saturn. Uranus and Neptune wold require a telescope. Venus and Jupiter have reliably good stretches of viewing in most any year. Mars has very good years, and not-good-at-all years (2011 and most of 2012 are poor for viewing Mars). Saturn will have a good year this year. Note that seeing the rings at will require a telescope, though - a 60mm at 170 power will do it.
687 days is a year for mars
Gallilio improved the telescope in 1609, one year after it was invented
a year on mars is 1.88 Earth years
year-round
"Year 'round" is the correct way to write it as it is a shortened form of "year-round".