Meaning
What does Earth chan mean?
Earth chan is the anime style humanoid depiction of planet Earth, portraying her as a cute blue and green haired anime girl, with a flat chest (something she is rather conscious about).
The flat chest joke is used to mock flat-earthers, who believe we are indeed flying upwards on a flat disk in space.
Earth chan is a clever incentive to raise consciousness in people about our home planet, that is sustaining and supporting us and that we tend to hurt.
Origin
What's the origin of Earth chan?
The idea of portraying Earth as an anime schoolgirl came from Twitter user @Trinimmortal, who shared the idea in 2017.
He proposed that someone makes an anime, depicting the planets going to school and bullying Earth for her flatness.
Soon after the original Tweet, user @felipecunhaeloi submitted his vision of the approach.
Spread & Usage
How did Earth chan spread?
The phenomenon had spread onto deviantART, where Earth chan was portrayed with a surgical mask on her face, while coughing.
Reddit has seen several approaches to Earth chan in the form of image macros, or fan created comics, like the one, where the character NASA is telling her that she is not flat.
Urban Dictionary added Earth chan to their archives in 2017, spreading the message of none other but Mother Earth.

External resources
- Fandom – Earth-Chan