He studied the observed color variations on Mars' surface and concluded that they were not seasonal or vegetational changes as most believed, but shifts in surface dust caused by windstorms.
Proučavao je promatrane razlike u boji površine Marsa i zaključio da nisu sezonske ili vegetacijske promjene o kojim se vjerovalo, nego smjene površinske prašine koje uzrokuju pješčane oluje.