By Wayne Boyd
Here the question said “planet” and not “exoplanet” and therefore I’m going to answer this in regard to our own solar system.
You could debate this answer in various ways, but I’m assuming here that we’re only talking about the 4 rocky planets, Mercury, Venus, Earth and Mars, since the gas giants really don’t have a solid surface. The gas giants are Jupiter, Saturn, Uranus and Neptune. So when you talk about how much surface area a planet has, I’m going to take it to mean the planet has a solid surface rather than just a planet made out of gas.
I’m going to say, then, out of the planets that have a solid surface, Venus has both the most surface area (even though Earth is bigger than Venus) and Venus also has the most destructive surface in our solar system. Some might say Mercury has the most destructive surface. We’ll compare that option later on.
Speaking of planets with solid surfaces, water is not a solid surface. Therefore, I’m also assuming we’re talking about a rocky planet but not the water on the surface. Earth has a lot of surface water. Since we didn’t count the gas giants because there’s no solid surface, I’m not counting the oceans, lakes and rivers because they are not solid surfaces either.
29% of Earth’s surface is solid land and 71% is covered with water. We need to calculate how much land that is, and to do that we’ll use square kilometers (km2). Most estimates put it just over 148 million km2. A couple put it just over 150 million km2.
Let’s just round it out at 149,000,000 km2. That’s 149 million square kilometers.
Surprisingly, Mars, which is much smaller than Earth but has no surface water, has a similar surface area to Earth. Mars has 144.8 million km2, almost as much as Earth. So Mars is competitive with Earth in land area. It’s also got a destructive surface because the atmosphere is very thin and has almost no oxygen. It’s poisonous to breath the atmosphere on Mars, but it’s not the most destructive of the four.
Of the four rocky planets, Mercury has the least surface area, which brings us back to Venus. Venus has no oceans, like Mars, and it’s bigger than Mars. Earth is the biggest of the rocky planets in our solar system. Venus is slightly smaller than Earth, but since there’s no oceans Venus has more solid land area. Venus clocks in with a whopping 460.2 million km2 of solid land. So Venus wins with the most solid surface area.
Now, I voted Venus as having the most destructive surface as well, but it’s a toss up with Mercury. The atmosphere on Venus is really harsh and it’s thick so the atmospheric pressure is equivalent to that of 3,000 feet underwater on Earth. It’s also 872 F (467 C), hot enough to melt metal, and it rains sulfuric acid. Again, we’re not talking about the gas giants because they don’t have a solid surface.
Mercury, on the other hand, has almost no atmosphere, but it’s close to the sun and the daytime temperature is 800 F, hotter than Venus. Night time temperatures are minus 290 F. But it doesn’t rain sulfuric acid like it does on Venus!
So I vote for Venus as the planet with the most solid surface area and the most destructive surface in the solar system. It’s still up to debate. Earth’s globe is bigger than Venus, but then again, if we don’t count the gas giants because they have no surface per se, then I figure we can’t count the oceans on our planet because they are liquid, so Venus wins in both categories.
The Russians have sent several probes to the surface of Venus. Here’s what it looks like.