He would die fast, Mercury shows no mercy.
Step out from behind the dark craters at the pole, where the cold hangs at minus 170 Celsius, and the transition slaps you in the face — Within ten kilometers of leaving the shadows, the sun would cook you.
A NASA spacesuit handles around 121 Celsius maximum – 430 Celsius on the surface of Mercury in sunlight; The math is easy. The suit is overwhelmed, the cooling system fails, your blood starts boiling.
The transition zone between eternal night and hell-day is narrow, no advance notice.
One second, heaters emit heat at usual rates. The next, they’re inundate, the suit becomes your heated coffin.
Maybe a quarter hour after that cooling stops, you’d be cooking in your own flesh — Brain death is quick at least, little mercy.
No one could cross Mercury on foot, the rovers would not even make it there.
The sun there is a hammer, not the gentle star we know on Earth – The fire is too near to Mercury, burns anyone who tries to walk its face.
