The space race is heating up, there are a few private enterprise spacecraft that have been unveiled and the Moon looks like a likely destination in the future. In the 1980`s we had a more hopeful vision of the future, it did not include terrorism and constant warfare. But with the successful docking of the first private spacecraft with the International Space Station, the future is looking rosy for space exploration. This article: http://www.deccanherald.com/content/266334/nuke-powered-spacecraft-mars-mission.html, has a proposal for a nuclear powered spacecraft that could reach Mars, a distance of 250,000,000 miles from Earth. That is greater than the distance from the Earth to the Sun, which is about 96,000,000 miles. But we would not want to be close to the Sun, due to the radiation. The movie Sunshine, got that wrong. We could send a probe to the Sun, there are plans for a carbon composite/foam space-probe to enter the corona and make observations of the conditions, but that probe will be protected by a sun-shield. The corona is less dense, so although it is hotter than the surface, the gas density is less, allowing the fragile craft to survive the heat.
Travelling to Mars would be a serious undertaking, the cost and the time involved in travelling to the Red Planet would require a massive investment from all major countries to fund that enterprise. Mars is an easier destination than the asteroid belt, that is a ludicrous distance, between Mars and Jupiter. If you could reach Mars and actually manage to gain a foothold with a base, then you could explore the Red Planet. Olympus Mons, the largest volcano in the Solar System would be a nice place to start. It is 29 Kilometres tall, so high that the top extends outside the atmosphere. Climbing it and looking out over the Tharsis bulge over the whole planet would be awesome. But we are spending 4,000,000,000 so far on the Iraq war and there are possibly more to come. If we had not wasted all of that money on that war we would have a Mars base by now. There are strange things in our Universe that we can not explain: http://www.securitronlinux.com/bejiitaswrath/giant-structures-in-space-swallowing-distant-galactic-clusters-is-this-another-universe/, huge structures in space that are swallowing whole galactic clusters for one.
They are likely to be concentrations of dark matter that have formed massively dense clusters of matter that draw in everything around them. Very strange indeed, we need to understand these strange structures more. There is a theory that gravity is leaking into our Universe from outside and that it is concentrated where mass is situated in the Universe. It is true that large planets distort space-time and cause a gravitational attraction, so maybe the mass of the planet sitting in space, causes gravity to accumulate. I always thought that it was the mass of the planet itself attracting matter. The Moon has a pull on the Earth and the Earth pulls on the Moon. The tides are caused by the gravitational attraction of the Moon pulling on the Earth, and the Earth itself also exerts a pull on the sun, this causes a minuscule wobble in the rotation of the Sun. That is how we can spot planets orbiting a foreign star, the parent star will be tugged on by it`s orbiting satellite and that causes the wobble that we can see from Earth. Another way is the rare occasion that the planet will be in between the star and our telescopes, we can see the star dimming slightly as it is occluded by the planet. This also allows us to look at the light that comes through the atmosphere of the planet and work out the composition. Such Stellar Spectroscopy is an invaluable tool for finding Ozone in the atmosphere, this is a good indicator of Oxygen.
Some people have a different theory about gravity: http://www.bringyou.to/apologetics/p67.htm, but this person is wrong. Jupiter does have rings, and the gravity of the Earth is perfectly sufficient to hold onto the Moon against the massive gravity of the Sun. The Moon is moving away from the Earth very slowly, but this is nothing to worry about. If people did a little more research with a good search engine, they would discover the actual facts instead of going out on a limb with a religious diatribe about how gravity is a fallacy. And there is dark matter, that holds the galaxy together. Some galaxies are so large they should fly apart, but they stay intact due to the presence of Dark Matter, which is an invisible glue binding them together. Dark Matter is a good explanation for the expansion of the Universe as well, the expansion is accelerating faster & faster, eventually trillions of years in the future, everything will have moved away from everything else and the Universe will be a very lonely place indeed. But we should not fear that, the Earth will be unable to support multicellular life in 300,000,000 years as the expansion of our Sun starts, which will become a Red Giant in a 5 Billion years, as it runs out of fuel. That is why the movie Sunshine got it wrong, the Sun would have gotten hotter as it ran out of fuel and swelled up, the Earth would have boiled instead of freezing. And you would have needed billions of the Stellar Bombs to restart the Sun.