Sometimes, regions of planet Earth light up with fire.
Since fire is the rapid acquisition of oxygen, and since
is a key indicator of life,
on any planet would be an indicator of life on that planet.
Most of the Earth's land has been
scorched by fire at some time in the past.
Although causing many a tragedy,
for many places on Earth
fire is considered part of a
natural ecosystem cycle.
Large forest fires on Earth are usually caused by
lightning and can be
visible from orbit.
Above, in the year 2000, stunned
elk avoid a
fire sweeping through
by standing in a river.