Compare to the Angus McKie art seen here. The skeleton in a spacesuit, representing the long dead astronaut, is a very powerful sci-fi trope that’s been around since the dawn of the genre. The decomposing explorer is often buried in sand and surrounded by a dead world. The attempt to colonize space, especially as a a result of escalating social upheaval or widespread devastation (i.e. a nuclear war) on Earth, is a deeply troubling idea to many and dates all the way back to the myth of Icarus.
The image is a warning against the hubris of flying too high, of crossing thresholds we were not meant to cross, of challenging God. Ray Bradbury’s The Martian Chronicles (1950) is a famous example of the theme, as are the early sci-fi films Rocketship X-M (1950) and Flight to Mars (1951), to name just a few examples.
I can’t find much information on Michael Gross. He has entries at the Internet Speculative Fiction Database under both Mike Gross and Michael Gross, for a combined ten cover works. Heavy Metal is not mentioned, but I know he did more than one cover for the magazine.
(Image via The Por Por Books Blog)
2 Warps to Neptune 
My did had this one in his collection, and the cover has always stuck with me: https://www.freedomsphoenix.com/Uploads/173/Graph/Inherit-The-Stars.jpg
Yup. Darrell Sweet, who did the Lord of the Rings covers for Ballantine in 1981.
Michael Gross also worked for National Lampoon in the 70’s. They were at one time publishers of Heavy Metal. He created the infamous “by this issue or we’ll kill the dog” cover.
Gross also illustrated the covers for the original Pocket Books editions of the Douglas Adams Hitchhiker’s Guide to the Galaxy books. The green laughing man was his creation.
*buy this issue. My goof!
I knew about NL but not about Hitchhiker’s. Cool. Do you happen to have a copy of those editions with the cover art credit listed? Maybe I can figure out how to update ISFD.
My source was Don’t Panic by Neil Gaiman, the Official Guide to the Hitchhiker’s Guide. I have various copies of Hitchhiker’s. I’ll look for cover art listings when I get home. I’m pretty sure the paperbacks and leather-bound editions (which reprint the covers in black and white) have his name credited to them.