differentiate between moon and asteroids
Answers
Explanation:
The Moon is closer to Earth, which reduces communications roundtrip times for teleoperation. It takes roughly 3 seconds for radio communications (or light) to travel from the Earth to the Moon and back. For asteroids, round trip communications takes much longer, e.g., minutes, thus requiring equipment to work much more autonomously, or people on-site at the asteroid to operate or supervise the equipment.
Human travel time is much less (though we've put people in space for more than a year already, and if we rotate the habitat for artificial gravity, they could stay much longer if they wished)
If anything goes wrong, it's more feasible to send a rescue or resupply ship to the Moon on an immediate response basis. It takes just a few days to get to the Moon, once the resupply vessel is ready, but could take weeks to get to the asteroid. (As for human rescue, this has been an extremely rare event over the course of more than 30 years of pioneering human spaceflight, and people go on riskier ventures to remote places on Earth full of different bacteria and unpredictable hazards...)
We are more familiar with the Moon at the present time, due to the Apollo missions and Lunar Prospector probe. We know little about asteroids, until probes go there. Over the next few years, starting in January 1999, probes will visit asteroids near Earth and give us good characterization of the surface material. Asteroid probes are also not terribly expensive, especially compared to the required mining and materials retrieval operation.
Lower cost. A smaller mission is required to retrieve asteroidal material to Earth orbit, since there is very little fuel spent on landing and relaunching from an asteroid's micro-gravity as compared to the Moon. This means launch of a smaller payload (fuel plus spacecraft) to go to any one of a number of asteroids near Earth. There are a number of known asteroids more accessible than the Moon in this way, and we're discovering more such asteroids frequently, largely due to the recent look-out for Earth-threatening asteroids and the new super-sensitive electronic sensors being mounted on a number of telescopes for this purpose.
Rocket costs and risks. Transport from the moon requires launch rockets. From asteroids, you need only low thrust interorbital rockets. No chance of crashing due to an imbalance in the rocket, or if your rocket engine fails. In fact, a cheap steam engine is sufficient for transporting asteroidal materials, thereby reducing the risk and complexity of the transport system, as well as the support infrastructure required.
Quality of material. The quality of asteroidal material is generally deemed superior to lunar material. Asteroids are generally rich in free metal (iron-nickel) and volatiles (water, carbon, others), though water ice has been discovered at the lunar poles in extremely cold craters. Less industry is required to process asteroidal materials into useful basic products than is required for lunar materials, in terms of both weight and complexity of equipment, for free metals at least. (Notably, the chances of something going wrong with the industry may be significantly less for asteroids, due to the simplicity of the equipment required to extract free metal and volatiles.) This "quality of material" category is an argumentative issue.
Fuel propellants. Needed for moving the material to Earth orbit, and for selling fuel propellants once in Earth orbit, asteroids can provide water (hydrogen and oxygen), carbon (e.g., for hydrocarbons), and other volatiles with a minimum of processing equipment (e.g., simple solar ovens). On the volatile-poor Moon, only oxygen is abundant everywhere, which must be extracted from dirt and rock minerals, though cold polar ice can supply hydrogen. The lunar ice is in permanent shadows so cold that it will be a bigger challenge to operate equipment there than on asteroids. On asteroids, you can also extract oxygen from dirt and rock minerals as on the Moon, but it's not necessary to do so because there are free volatiles on asteroids at temperatures much more manageable for equipment -- hydrogen as well as carbon and other volatiles. For lunar materials utilization, with the exception of the lunar polar ice, either part of the fuel must come from Earth (or from asteroids) or else new propellant technologies must be developed (e.g., powder aluminum rocketry, requiring research and development as well as manufacturing capability on the Moon). This may be the murkiest of the issues due to the lunar poles.
There's only one Moon in our night sky, and there may be more international debate by many cultures on its exploitation and environment. As regards the countless asteroids, they aren't so special.