No spacesuit. No oxygen. Just you, dropped on a random world. How long do you last?
Assume you are a healthy adult human, suddenly dropped without a spacesuit.
Humans are absurdly fragile. Earth is the only planet in the solar system where you can step outside and not immediately die. On every other world, the problem is not "how uncomfortable" but "which specific death happens first."
On Venus, the surface is 462°C — hot enough to melt lead. The pressure is 92 times Earth's atmosphere. You would not burn to death slowly. You would be crushed and incinerated simultaneously, in under a second.
On Jupiter, there is no surface. You would fall through gas that gets denser and hotter. About 1,000 km down, the pressure would crush your body into something unrecognizable. You would not even hit "ground" — you would just get squeezed until you merged with the atmosphere.
On the Moon, the problem is simpler: there is no air. You would hold your breath for about 15 seconds before losing consciousness. Total survival time: roughly 90 seconds if you don't exhale (which you must — your lungs would rupture otherwise).
Mars is the friendliest killer. The air is too thin to breathe, and the temperature averages -63°C. But if you had 15 seconds of oxygen, you could survive about 2 minutes before the cold and vacuum got you. It's the closest thing to survivable outside Earth. It still kills you.
Without a spacesuit, the vacuum of space causes ebullism — the boiling of body fluids at low pressure. Your saliva would boil off your tongue. You would lose consciousness in 15 seconds. Total survival time is about 90 seconds, assuming you exhale to avoid lung rupture.
Heat and pressure simultaneously. 462°C is hot enough to melt zinc. The atmospheric pressure is 92 bars — equivalent to being 1 km underwater. You would be crushed and cooked in less than a second. The sulfuric acid clouds above you are the least of your problems.
No. Mars has 0.15% of Earth's atmospheric pressure. An oxygen mask would give you air, but your blood would still boil from the vacuum. You need a pressure suit, not just oxygen. Mars is the closest planet to Earth, and it still kills you in minutes.
You would not reach the Sun's surface. At a distance, you would burn. The Sun has no solid surface — it's plasma. Falling in, you would incinerate long before reaching the "photosphere." Survival time at the Sun's visible surface: 0 seconds.