The sky's the limit for trailblazing meteors

Meteors may be leaving far more "kiss marks" - their blazing trails - on the earth's atmosphere than previously believed, says a new study by Chinese scientists.

The researchers have picked up numerous radar echoes of meteor trails at altitudes as far out as 170km above the earth's surface - more than 30 per cent higher than was previously thought possible for atmospheric density to produce the effects.

Meteroids are objects travelling through space. They become meteors when they enter the earth's atmosphere, typically at 20km/s, producing enough friction to cause streaks of light from aerodynamic heating. Remnants of meteoroids that withstand the blast-furnace-like conditions of atmospheric entry to hit the ground are called meteorites.

"We are very excited by the findings," said Dr Li Guozhu , an associate researcher at the Chinese Academy of Sciences' Institute of Geology and Geophysics and lead scientist on the international study.

"A long-standing debate can now be settled."

A meteor had to come "intimately close" to leave a mark in the sky, at the boundary set -arbitrarily, it seems - at 130km above the earth. The limit was set partly because of a lack of observable data at higher altitudes, and also by laws of physics.