Re: What types of anti-meteor weapons are used on the moon?

What types of anti-meteor weapons are used on the Moon?

There are no anti-meteor weapons used on the Moon. In fact, the Earth has no artificial anti-meteor weapons either. The only “weapon” protecting the Earth from frequent micrometeorite impacts is the atmosphere. Small meteors (about 1--10 grams in mass down to almost a nanogram (0.000000001 gram)) burn up in the Earth’s atmosphere before reaching the ground. Extremely small-sized particles (very fine dust) can make it through the atmosphere unmelted. Meteors larger than about 10 grams are partly melted, but the interior reaches Earth’s surface intact. The atmosphere would not be able to stop large meteors from striking the surface. Proof of this lies in craters found on the Earth’s surface, such as Meteor Crater in Arizona and Chicxulub on the Yucatan Peninsula in Mexico (the impact that is believed to have caused the extinction of the dinosaurs and many other species about 65 million years ago). Since the Moon has no atmosphere, there is no protection from even the smallest meteors.

The astronauts that landed on the Moon did leave behind several instruments, including seismometers and lunar ranging retroreflectors. The seismometers are used to measure seismic waves, which can be produced by both natural and artificial sources. Natural sources of seismic waves include “moonquakes” and meteorite impacts. Artificial sources include the ascent and landing stages of several lunar modules, and the third stages of Saturn 5 rockets (the rockets used to launch the Apollo missions into space), which were deliberately crashed into the Moon to produce vibrations to be measured by the seismometers. Seismometers allow for the determination of the internal structure of the Moon, as well as the knowledge of whether or not the Moon is seismically active (are there moonquakes, and if so, how many, and how powerful?). Seismometers were left on the Moon by the Apollo 11, 12, 14, 15, and 16 missions. The seismometers from Apollo 11 only returned data to Earth for 3 weeks, but the other seismometers continued to transmit data until 1977 (they were all placed on the Moon between 1969-1972).

The retroreflectors can be thought of as special mirrors on the Moon’s surface. These mirrors can be illuminated by a laser beam aimed by a large Earth-based telescope. Aiming the laser at one of the reflectors on the Moon is similar to using a rifle to hit a moving target the size of a dime two miles away. The beam is reflected off of the mirror and returns to Earth, where it can be observed by another telescope. This laser beam provides a 2-way travel time, which can be used to determine the distance to the Moon, with an accuracy of about 3 centimeters (1.2 inches). Measurements can be taken over time, and it has been determined that the distance between the Earth and the Moon is increasing slowly, currently at a rate of about 3.8 centimeters per year. Retroreflectors were placed on the moon by the Apollo 11, 14, and 15 missions.

Here are some websites for further information:

• Passive Seismic Experiment;

• Apollo Laser Ranging Experiment; and

• Lunar Ranging Retroreflector Experiment.