Although skeptics require other evidence to confirm either of these theories, some of the following scenarios may explain the Marfa lights.
1. Car Lights
In the early 2000s, physics students from the University of Texas (Dallas) investigated the viewing platform's proximity to Highway 67, theorizing that headlights were behind the phenomenon. They conducted several experiments and found that with each car passing, something resembling Marfa lights appeared simultaneously.
Although this revelation seems to close the case quickly, it doesn't account for the first recorded sighting by a white settler in the area.
In 1883, young cowhand Robert Reed Ellison witnessed Marfa lights near Paisano Pass. This predates the first cars to arrive in Texas by 16 years, as well as the construction of Highway 67 by roughly four decades.
2. UFOs
Flying saucers or other unidentified anomalous phenomena (UAP) may explain the Marfa lights. However, many skeptics often point to the viewing area location being so close to a World War II airfield that supported thousands of servicemembers between 1942 and 1947.
This is not to say that the military hasn't traditionally remained tight-lipped about potential extraterrestrial activity. Although you would expect that some information would have been released by now.
3. Atmospheric Phenomena
Natural gas leaks mixing with the sun and air to cause a chemical reaction similar to St. Elmo's fire is a common scientific explanation that many skeptics hold. However, no one has ever been close enough to Marfa lights to test this theory.