Because a nuclear meltdown can be caused if systems fail.
Answer:
<em>The amount of water in circulation is the same</em>
Explanation:
The water cycle is the pathway in which water moves from the atmosphere to the earth and back to atmosphere ones again.
During the sunny period, the temperature of the earth is heated up, water evaporates to the atmosphere as water vapour. The water vapour gathers as cloud and comes back to the earth as rain, which enters our rivers and stream. Thereby maintaining a continuous cycle.
With the water cycle, the movement of water via precipitation and evaporation is the same on earth.
Mars is the focus of much scientific study about possible human colonization. Its surface conditions and the presence of water on Mars make it arguably the most hospitable of the planets in the Solar System, other than Earth. Mars requires less energy per unit mass (delta-v) to reach from Earth than any planet except Venus.
Permanent human habitation on a planetary body other than the Earth is one of science fiction's most prevalent themes. As technology has advanced, and concerns about the future of humanity on Earth have increased, the argument that space colonization is an achievable and worthwhile goal has gained momentum. Other reasons for colonizing space include economic interests, long-term scientific research best carried out by humans as opposed to robotic probes, and sheer curiosity.
One of Elon Musk's stated goals through his company SpaceX is to make such colonization possible by providing transport, and to "help humanity establish a permanent, self-sustaining colony on Mars within the next 50 to 100 years".
Many organizations support the colonization of Mars. They have also given different reasons and ways humans can live on Mars. One of the oldest organizations is the Mars Society. They promote a NASA program that supports human colonies on Mars. The Mars Society have set up Mars analog research stations in Canada and the United States. All other organizations include MarsDrive, who wants to help fund settlements on Mars, and Mars to Stay. Mars to Stay advocates settlements on Mars. In June 2012, Mars One released a statement that they believe could help start a colony on Mars by 2023.
