and renaming the categories: in particular, Level 1 was changed from "Events meriting careful monitoring" to "Normal". The Torino Scale has served as the model for the Rio scale which quantifies the validity and societal impact of SETI data. Current Torino scale The Torino Scale also uses a color code scale: white, green, yellow, orange, red. Each color code has an overall meaning: No incoming object has ever been rated above level 4, though over all of Earth's history impacts have spanned the full range of damage described by the scale. Actual impacts and impact energy comparisons The Chicxulub impact, believed by most scientists to have been a significant factor in the extinction of the non-avian dinosaurs, has been estimated at 100 million (108) megatons, or Torino Scale 10. The impacts which created the Barringer Crater and the 1908 Tunguska event are both estimated to be in the 3–10 megaton range, corresponding to Torino Scale 8. The 2013 Chelyabinsk meteor had a total kinetic energy prior to impact of about 0.5 megatons, corresponding to Torino Scale 0. Between 2000 and 2013, 26 asteroid impacts with an energy of 1–600 kilotons were detected. The biggest hydrogen bomb ever exploded, the Tsar Bomba, was around 50 megatons. The 1883 eruption of Krakatoa was the equivalent of roughly 200 megatons. The comet C/2013 A1, which passed close to Mars in 2014, was originally estimated to have a potential impact energy of 5 million to 24 billion megatons, and in March 2013 was estimated to have a Mars impact probability of ~1:1250, corresponding to the Martian equivalent of Torino Scale 6. The impact probability was reduced to ~1:120000 in April 2013, corresponding to Torino Scale 1 or 2. Objects with non-zero Torino ratings Currently non-zero (diameter ~48 meters) with a 2.0 day observation arc shows a 1 in 830 chance of impact on 14 February 2046. The nominal distance from Earth on 14 February 2046 is with a 3-sigma uncertainty region of about ±21 million km. Downgraded to zero This is a partial list of near-Earth asteroids that have been listed with a Torino Scale rating of 1+ and been lowered to 0 or been removed from the Sentry Risk Table altogether. Most objects that reach a Torino Scale of 1 have a short observation arc of less than 2 weeks and are quickly removed as the observation arc gets longer and more accurate.