A half-ton Soviet-era spacecraft stuck in orbit for 53 years is expected to make an uncontrolled plunge back to Earth any day now.

A Soviet-era spacecraft launched in the 1970s is expected to make its return to Earth sometime this weekend. The unmanned robotic spacecraft, Kosmos 482, originally set out to land on the scorching surface of Venus but it never completed its mission. Instead, it’s been stuck in Earth’s orbit for over 50 years.

After all this time, the half-ton object, about the size of a concert grand piano or a male polar bear, is finally expected to make an uncontrolled plunge back to Earth. The problem is, experts aren’t exactly sure when — or where — it will land. (Yikes.)

Yahoo News spoke with Jonathan McDowell, an astronomer at the Harvard & Smithsonian Center for Astrophysics, about what we do know about the object and whether we should be worried. His responses below have been lightly edited for length and clarity.

Yahoo News: What is Kosmos 482? Why was it launched and how did it get stuck in the first place?

McDowell: It was originally meant to be the Soviet probe, Venus 9 [that would travel to the surface of Venus]. They launched it in March 1972, along with Venus 8. The rockets put their space probes in parking orbit around the Earth, and then fired the upper stages to send them out toward Venus. Venus 8 got to Venus.

But the upper stage for Venus 9 broke down halfway through its rocket firing, stranding the probe in orbit around the Earth. Rather than admit that they'd had a failure, the Soviet Union said “Oh, we just launched another Kosmos satellite. It's totally fine. We're calling it Kosmos 482. Nothing to see here.”

That is like their standard practice. They're now up to Kosmos 2500-something. They throw all their military satellites in there, but also their failures that they don't want to admit.

Kosmos 482 has been stuck in orbit for 53 years. Why is it returning to Earth now?

There were a few pieces [of Kosmos 482] left in orbit. There was the rocket stage, there was the main part of the Venus probe, and there was this half-ton sphere that was meant to be the thing that would enter Venus's atmosphere and survive to the surface.

Every time these things go around the Earth, they skim the atmosphere and lose a little bit of energy. So they don't go quite so high up the next time. The orbit shrinks over time until eventually the [objects] reenter.

Two of the [three] objects reentered in the early 1980s, and there was this one object left that didn't seem to be affected as much by Earth’s atmosphere.

After 50 years of this going around the Earth every few hours, it has lost enough energy for its orbit to shrink enough that now it's on the verge of reentry.

When is it supposed to crash onto Earth?

Sometime over the weekend, it's going to get low enough that it can no longer orbit and the atmosphere is too dense. It will slow down rapidly and crash onto the Earth.

How heavy is the object and how fast will it crash into Earth? Does it have a parachute deployment system to slow it down or anything?

After 50 years, the batteries are stone cold so there’s no way the parachutes will work.

[The object weighs] half a ton. It’s traveling at 17,000 miles an hour, just like everything else in low Earth orbit. But once it reenters, you'll see this big fireball, and that is the speed energy getting converted into heat energy.

The heat shield may protect it from burning up and melting during reentry.

It can't fly through the air at 17,000 miles an hour. As it gets dense enough in the atmosphere, [the object] slows down really rapidly because of this enormous headwind. That speed gets converted into heat, and everything slows down. Once it crashes down to the lower atmosphere, it'll only be going at a couple-hundred miles an hour.

Is there a guestimate as to where this thing will land?

Somewhere between London in the north and the Falkland Islands in the south (off the east coast of Argentina in the South Atlantic Ocean).

So somewhere between 52 degrees north and 52 degrees south. If you're in Scotland or northern Canada or Antarctica, it's not going to come over you. Pretty much anywhere else is still in the frame.

Until we can know exactly when it's coming down, we won't know where because if you're an hour off, you're 17,000 miles wrong. This is always true with uncontrolled satellite reentries. We never know where they're going to come down until after the fact.

So ... should we be worried?

Because the Earth is a big target, the chances that it’s going to come down near you is tiny. Most of the Earth is ocean, but maybe we'll be unlucky and it’ll hit land.

Even today, most land is unoccupied, so the chance that it will hit a person is very small. It's not zero, but it's small.

I think any one satellite reentry hitting someone is super unlikely, but we're having so many of them now that we're kind of rolling the dice each time, and eventually we're going to get unlucky.

Wait — what? How often do satellites come down from space?

We get about three a day. Most of them are small enough that they melt entirely, burn up and don't reach the ground.

Every month or so we get a couple that are going to leave something reaching the ground. Usually they fall over the ocean. Every few months, we get a case where we found a bit on the ground that's from the satellite reentry.

What makes this object different from other space junk that has crashed into Earth?

What's unusual about this object is that it’s designed to survive Venus, which has utterly hellish conditions. It was over-designed for surviving a reentry into Earth's atmosphere. Mind you, it's been in space for over 50 years, so whether the heat shield is still pristine or not, is unclear.

Normally what happens is the satellite will melt, even if it doesn't completely burn up, and it will break into chunks. Even if they survive to the ground, they'll be strewn over several hundred miles of reentry track. So there's not much in any one place. But for this [Kosmos 482 object], it's going to come down in one half-ton lump, most likely. So that'd be bad if there's anyone underneath.

What happens if this half-ton piece of Soviet-era spacecraft damages a building or a house when it crashes onto Earth? Who’s liable?

One thing that's important to know about is the liability convention, which is part of space law. Suppose this crashes into some building in the U.S., or into your garden shed. What do you do? The U.S. government talks to the Russian government and says, “We have a bit of your space debris under the liability convention. You're entitled to have it back, but you're also liable for any damage that it caused.”