Definition: Rewrite each original sentence in order to make it easier to understand by non-native speakers of English. You can do so by replacing complex words with simpler synonyms (i.e. paraphrasing), deleting unimportant information (i.e. compression), and/or splitting a long complex sentence into several simpler ones. The final simplified sentences need to be grammatical, fluent, and retain the main ideas of their original counterparts without altering their meanings.
Input: A dark albedo feature about across has been named Olbers in honour of Vesta's discoverer, but it does not appear in elevation maps as a fresh crater would, and its nature is presently unknown, perhaps an old basaltic surface.

The dark electromagnetic radiation feature has been named Olbers in honour of Vesta's discoverer. A fresh crater would show in elevation maps but this crater does not, so it's origin is unknown.