The following is an excerpt from Mars Microphone: Ready to Go by Greg Delory, describing the Mars Microphone instrument.

The Mars Microphone is a small device, roughly 5 centimeters on a side and one centimeter thick (2 x 2 x 0.5 inches), weighing less than 50 grams (1.8 ounces) and using a small amount of power, less than 0.1 watt during its most active times. In addition to the microphone, the instrument contains digital electronics to acquire and store sound samples. Because the rate at which we can acquire data will be limited, it will take several days, maybe even a week, to retrieve one 10-second sound clip. The device has internal memory, similar to the RAM in your home computer, which will store sounds for transmission to Earth along with other lander data.

In the construction of the Mars Microphone, we relied on commercial, off-the-shelf technology, meaning that very few of the components were developed specifically for this mission. Most are readily available commercially. Our sound processor chip , for example, is also used in talking toys and educational computers that listen and respond to spoken words. The microphone itself is typically used in hearing aids. The entire program, including design, construction, and testing, cost roughly $50,000, a bargain for an instrument on a planetary probe.

The Mars Microphone has since passed several tests to show it can withstand the rigors of a planetary mission. Radiation levels in space and on Mars are higher than what we are used to on Earth, and, like humans, the electronic components in the microphone are sensitive to radiation damage. We exposed the microphone and the sound processor chip to levels of radiation that they would receive during the mission, and there were no failures or degradation of performance. We also conducted thermal tests with temperature ranges of -100 to +20 degrees Celsius (about -150 to +70 degrees Fahrenheit), and detected no malfunctions.

Finally, we performed pressure tests to ensure that the microphone could actually hear noises at the low pressures of the Martian atmosphere. Although sound level diminishes substantially with decreased pressures, we were still able to hear sounds by increasing the gain of the amplifiers within the microphone.

The microphone was integrated onto the Mars Polar Lander last October at Lockheed Martin in Denver, Colorado. We verified that the microphone worked properly on the lander and even listened to the technicians conversing as they tended to the craft.