A controversial study by researchers at the University of Florida and Carnegie Institution theorizes that space dust in Earth's atmosphere and changes in the planet's orbit may have started the gradual extinction of dinosaurs and other life thousands of years before a massive asteroid collision dealt the final blow.

Currently, Earth is accumulating about 30,000 metric tons of cosmic dust from interplanetary space each year. The scientists found that most of this dust comes from just three families of asteroids (Eos, Themis, and Koronis) in the solar system's asteroid belt. As Earth orbits the sun, it passes through this cloud of dust particles, capturing some of the dust in its atmosphere. The study showed that the amount of dust captured depends on the shape (ellipticity) and tilt (inclination) of the Earth's orbit. These vary periodically due to the gravitational pull of other planets. The dust buildup rises and falls in about 100,000 periods that correspond to ice-age cycles.

Space dust could remain at high levels in the atmosphere for periods of thousands of years, and any associated cooling would also persist for this length of time. If the amount of dust in Earth's atmosphere altered the climate, the change would cause gradual extinction.