91探花 scientists recently published the first large-scale survey of impurities in North American snow, to see whether they might absorb enough sunlight to speed melt rates and influence climate. The project involved collecting hundreds of snow samples from 67 sites away from any cities or major roads. The trip took the researchers from Seattle to North Dakota to Churchill, Manitoba. Every few days they melted and filtered the snow in their motel rooms, then back at their 91探花lab they shone light through a filter to see how much light was blocked, and did chemical analyses to determine what particles were responsible.