---
author: Eric Wagoner
date: '2002-07-24T09:55:14'
description: The Palermo Scale is used by astronomers to measure the risk imposed
  to earth by an asteroid. It's a logarithmic scale with values ranging (roughly)
  from -7 to +7. Anything less than -2 can be ignored, and those between -2 and zero
  merit careful monitoring. For the first time, an object with a value greater than
  zero has been discovered.
draft: false
title: Impact threat
---

[The Palermo Scale](http://www.jpl.nasa.gov/neo/risk/doc/palermo.html) is used by astronomers to measure the risk imposed to earth by an asteroid. It's a logarithmic scale with values ranging (roughly) from -7 to +7. The specks of dust that hit us every day are at the low end and the dinosaur killer-type would be at the high end. Anything less than -2 can be ignored, and those between -2 and zero merit careful monitoring. For the first time, [an object with a value greater than zero](http://news.bbc.co.uk/2/hi/science/nature/2147879.stm) has been discovered -- 0.06. Further observations will modify this, hopefully back into negative territory. I went to post this to MetaFilter, but they're [already on the case.