Earthwards means towards the Earth’s surface — the same idea as earthward. A meteor can streak earthwards; from a high ridge you may look earthwards at the fields. British English often likes the -wards form for this kind of adverb (like towards, afterwards, homewards), while American English more often drops the s. The meaning does not change with the s. It is still a somewhat literary or technical word; everyday speech prefers down or towards the ground. Though actually, from space it means towards the planet as a whole, not only “down” relative to your feet.