Terra incognita refer to the hypothesized continent Terra Australis Incognita ("The unknown land of the South"), as seen in the Theatrum Orbis Terrarum map by Abraham Ortelius (1570). During the 19th century "terra incognita" disappeared from maps of the earth, since both the coastlines and the inner parts of the continents had been fully explored. But the bottoms of the seas remain mostly un-mapped, as do many other land surfaces in the solar system. The phrase is now also used metaphorically by various researchers to describe any unexplored subject or field of research. For more history of the terms, see Terra Australis,
The Magic School Bus Lost in the Solar System the book. Most notably, in the episode, Janet's bragging about herself does not appear to be empty bragging and she constantly raves about how "proof" is needed for all extraordinary claims, prompting her to force Arnold to collect "proof" from every planet in the solar system, so she can prove to the students in her class that she actually traveled to all the planets. Also in this one Arnold surprisingly suggests going to outer space himself to prove to Janet the truth. Also, instead of remaining in the asteroid belt, Ms. Frizzle uses her jet pack to fly off to