Q: We use salt here on Earth to melt ice on our sidewalks and streets. Would it be possible to use a similar technique to melt Marsí polar ice caps? - Jennifer
A: Adding salt to water lowers its freezing point. This would be true on Mars as well as on Earth. The lowest that a salt salution can lower the freezing point is what is called the eutectic point. For ordinary salt (sodium chloride) the eutectic point is about -20C (about 0 F). Since the temperature on Mars is well below this (average is -60C), this salt will not allow melting on Mars.
Q: How long would it take to make a phone call from Mars to Earth? - Ben Bern
A: It takes a signal 12-20 minutes to travel each way when Mars is on the same side of the Sun as us. Phone calls as we know them cannot be made to Mars with this kind of delay.
Q: When man begins the process of terraforming Mars there will most likely be protestors that want to keep Mars as it is. How will we cope with that? - Brett
A: When terraforming Mars is seriously proposed by Martian settlers, debate will rage all over both planets. Terraforming will probably still continue by the settlers who will benefit from it the most. Some compromises can be made, such trying to limit the thickness of the atmosphere, thereby keeping areas at high elevations mostly pristine. But such limits are not a solution, even if we really did have the technological ability to enforce them. In the end it will be the first generations of Martians who will decided what happens to Mars. And while terraforming Mars will certainly change the planet significantly, the many years that terraforming will take will give much time for the current beautiful, but lifeless, Mars to be explored through the eyes of artists and scientists.