Original post here. This image was researched by Bacchus at ErosBlog as part of the “Γ commission.” The research was originally published at Hedonix as “Γ 027 Cute Space-Girl.” Here is what Bacchus found.
Appearances of this image on Tumblr all trace back to this post on Cartoon Retro. Although that Tumblr offers little in the way of self-explanation, it turns out to be the Tumblr of cartoonist and designer Shane Glines, who also uses cartoonretro as his DeviantArt ID where he claims the Cartoon Retro Tumblr as his own in the bio there. A perusal of his DeviantArt gallery (where this image does not appear) does offer exemplars (such as this one) of his artistic signature, which is a sort of stylized S followed by an indistinct dot or glyph and which can be seen in the subject artwork. Thus, even though Glines appears to post a variety of images to his Tumblr from various sources, it seems confirmed that the subject cartoon is one of his.