During the planet's "great opposition" of 1877, he observed a dense network of linear structures on the surface of Mars, which he called canali in Italian, meaning "channels", but the term was mistranslated into English as "canals".

In his book Life on Mars, Schiaparelli wrote: "Rather than true channels in a form familiar to us, we must imagine depressions in the soil that are not very deep, extended in a straight direction for thousands of miles, over a width of 100, 200 kilometres and maybe more.

I have already pointed out that, in the absence of rain on Mars, these channels are probably the main mechanism by which the water (and with it organic life) can spread on the dry surface of the planet."

An observer of objects in the Solar System, Schiaparelli worked on binary stars, discovered the large main-belt asteroid 69 Hesperia on 29 April 1861,[7] and demonstrated that the meteor showers were associated with comets.

He was the first to realize that the concentric spheres of Eudoxus of Cnidus and Callippus, unlike those used by many astronomers of later times, were not to be taken as material objects, but only as part of an algorithm similar to the modern Fourier series.