There are reports of mysterious lights that can be seen on a clear night across Mitchell Flat, an uninhabited desert area southeast of Marfa, Texas. Speculations have flourished as to the origin of these so-called Marfa Lights.

Designed by Marfa High School Gifted and Talented students and supported by the Texas Department of Transportation, a viewing platform was built 2001 alongside Highway 90 from Marfa to Alpine, 14 km east-southeast of Marfa. Every clear evening, people gather there to watch the Marfa Lights which have become a tourist attraction.

Mitchell Flat lies slightly lower than its surroundings, therefore straight paths exist from the observer to very distant points. In the evening, warm air close to the ground is sometimes superimposed by cool air. This causes refraction, i.e. the path of the light is bent, resulting in mirroring and blurring of distant lights.

In the old days, the lights may have been campfires. Nowadays, there is nothing mysterious about Marfa Lights. The lights come from nearly 20 km away vehicles driving on Highway 67 from Marfa to Presidio. Consider the above sequence of three photographs, taken with 10 s intervals. Several white lights are moving to the right, i.e. towards Marfa, while a few red lights are moving to the left, i.e. towards Presidio. The angle between the highway and the viewing direction is such that of vehicles moving from Presidio to Marfa, only the headlights can be seen, and of vehicles moving in the opposite direction, only the tail lights.

The red light to the left is a blinking beacon of the nearby Marfa Army Airfield. The lower red light is a reflexion on the tarmac. Slightly right of the middle of the image is a stationary bluish light of unknown origin. A ghost light anyhow?

The image below is composed of 15 photographs with 2 minutes exposure time each, making the total exposure time half an hour. There was full moon, but the moon was intermittently obscured by clouds. Since the photographs were merged in lighten only blending mode, the whole scene appears moonlit. Although the first photograph was taken during astronomical twilight while the sun was 14 degrees below horizon, afterglow can still be seen. It is weaker on the subsequent photographs, but due to the chosen blending mode, the brighter afterglow of the first one predominates.

Now consider the interrupted light trace of the moving vehicles. Why isn’t there a single light trace across the image? Obviously, the area beyond Mitchell Flat is hilly, such as there not always exists a straight path between the highway and the observer at the viewing platform.

Slightly left of the middle of the image, close to the horizon, is a tiny white light (visible on all single photographs) of unknown origin.