Our smallest neighbor continues to shrink, like your great-uncle who was 5-foot-4 and 125 pounds the last time you saw him.
No offense to your uncle. There's nothing wrong with being 5-4, 125. But if you used to be 5-8, 175, that's a fair amount of shrinkage. If you disagree, ask Mercury.
The innermost planet in our solar system is not only shrinking (shrinking!), it's shriveling at a faster rate than previously thought. It's like Mercury took GLP-3 drugs and is now back to the same size it was when it was a high school sophomore.
Scientists working at the German Aerospace Center's Institute of Space Research (which those of us in the space game called GACISR, pronounced "Gack-us-sir) – last month said that Mercury was shrinking at as much as a 30% faster rate than previously thought and that it had lost up to 14 miles in diameter. That's the greatest loss in diameter since Adele or John Goodman dropped weight, depending on which offends you less.
Part of the planet's size loss is due to constant bombardment by debris, similar to the plight of bad performers during Vaudeville (a 100-year-old pop culture reference!). But the bigger impact of that bombardment is that it hid the loss of size, kind of like wearing a Mumu after you've dropped 20 pounds on a starvation diet.
Very few spacecraft have visited Mercury, mostly due to the planet's high temperature and concern over getting Mercury poisoning (get it?). To be fair, part of the reason for our lack of visitation is also due to Mercury's terrible tourism advertisements, which proclaim "come to Mercury and see if you can survive 0.000001 seconds in our toxic atmosphere!"
Mercury has been shrinking since its formation, 4.5 billion years ago. That's because it has an incredibly hot core (Mercury's core is the same temperature as pizza sauce fresh out of the oven). The heat isn't what makes it shrink; it's the cooling, which is only due to the heat, so never mind.
As the hot core has cooled over the millennia and megaanna (a new word! It means millions of years), the mantle and crust (another similarity to pizza sauce: Mercury's core touches a crust!) keep tightening, making the planet like someone wearing Spandex pants that are two sizes too small.
The concern is that Mercury could either get so tight that it explodes or shrink so much that it needs help to reach the top shelf to get a Mars bar (planet joke! The first-ever planet column I've written without a "Uranus" joke!)
On the other hand, Mercury is only about 3,000 miles across, so the14-mile shrinkage is the equivalent of a 200-pound person losing nearly a pound. Maybe it's not a big concern.
But scientists seem excited and fascinated. They haven't been this engaged since they kicked Pluto out of the solar system for gambling (I can't remember if that's the cause, but I think so).
An article on Mercury's shrinkage, published by NBC, quoted Japanese scientist Gaku Nishiyama, who is part of a team researching Mercury. “We are quite excited,” Nishiyama was quoted as saying, adding that “we are approaching the reality of Mercury’s evolution.”
Here's the reality of Mercury's evolution: Like most things that get really old, it is shrinking. Unless I'm badly mistaken, I suspect Mercury also is having a harder time hearing conversations in busy restaurants, has to get up in the middle of the night to go to the bathroom and often wonders what caused various aches and pains.
I hope Mercury doesn't merely waste away to nothing, but it's had a 4.5-million-year run, which is pretty good. And when you think about it, if you have to lose a planet, would you rather use Mercury or Uranus?
I was so close to breaking the Uranus joke streak!
Reach Brad Stanhope at bradstanhope@outlook.com.






