Space scientists are keeping a close eye on a ‘green comet’ fast approaching the Earth – reaching its nearest point to us on February 24. Comet Lulin will streak by the earth within 38 million miles — 160 times farther than the moon -and is expected to be visible to the naked eye. Discovered only a year ago, the comet gains its green color from poisonous cyanogen and diatomic carbon gases in its atmosphere.