Terahertz

Photonics Briefs – Martian Snow

One of my friends is amicably known as the "Martian weather girl," as her job, with the Canadian Space Agency (CSA) is involved with plotting weather trends around the Phoenix lander, as well as analyzing the Martian soil for various salts.

Knowing someone like this gets you the knowledge, that apparently kept quiet by our government, that there is snow falling on Mars.

Now, to bring this to photonics, let's look at the technique of LIDAR that was used to detect the falling atmospheric snow. Unfortunately the snow vaporizes before it reaches the ground, so there won't be any snow-Martians.

LIDAR stands for "LIght Detection And Ranging" and relies on firing laser pulses into the sky and looking for bits that are reflected back by debris in the atmosphere. It's analogous to when you shine a laser or flashlight into the fog and some of it gets scattered back at you.

The principle is fairly simple, and the only difficulty lies in collecting the scattered laser pulse. Luckily, signal-to-noise is greatly improved with the use of coherent laser pulses, so you at least know when you are seeing something.

That's all for this week.