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, which is not practical for a phone call. However, currently it is impossible to send a signal to Mars when it is on the other side of the sun. Communication with Mars will need to be done by sending recorded “letters” (video, voice, written) and later receiving a reply in a similar way. - Daniel Slosberg

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 this century I predict that debate will rage all over both planets. Personally I believe that terraforming will go ahead anyway by the settlers that will benefit from it but compromises can be made; one of many ideas is to have a height limit: anything above six kilometers above datum can be left near pristine while lower altitudes can enjoy tolerable pressures and temperatures. In the end it will most likely be up to the Martians to decide, and their vested interest will likely be more terraforming oriented. - Felix

	Solar sail. Visit The Planetary Society to learn about their solar sail project, Cosmos 1.

Q: Could the idea of using light craft to go to Mars become a reality? If I were to use a light craft to get to Mars, I would put the laser that emits the light to the craft on the bottom of the craft. The laser would not get weaker as the space vessel gets further away from the laser source. Have people thought about using light craft as space travel to Mars, and can the laser be attached to the space vehicle instead of the space station? - Andy Staudacher

A: In principle, any mission beyond Earth’s orbit could be powered by a “light craft” propulsion system, but the major problem is that we do not have the kinds of lasers that would be needed to power such a craft. These lasers would have to be incredibly powerful, practically “Death Star” lasers and would therefore require not only enormous construction facilities in space, but also an incredible power source. The biggest problem with placing the laser on the ship traveling to Mars would be that the laser would have to be huge, and require a vast energy source. If we consider where this energy were to come from, there are really only two possibilities: a nuclear reactor, either fission or fusion, or perhaps controlled micro antimatter detonations. However, if we were able to build these types of reactors, it would be much easier to just use them as a means of propulsion by themselves, rather than tie them into a massive laser. For example, fission reactor engine prototypes in the 70s used the fission of uranium or plutonium to heat up hydrogen gas until it is in a plasma state (all the electrons are sheared off) and then expel it through a nozzle at the back of the ship, thereby producing thrust.

Unfortunately, one of the main reasons we have not actively pursued nuclear power technology for space missions is the possible explosion and crash of the rocket during takeoff, thereby spreading radioactive debris over large areas of the Earth and creating an ecological disaster. In other words, while light craft and other forms of exotic propulsion are in principle feasible, we will make many flights using conventional chemical rockets to Mars before we have the infrastructure to construct exotic and perhaps more efficient propulsion systems. - Luke Colby

Ask a Mars question and it will be answered in the next issue of The Martian Chronicles!