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Humans have done a rather remarkable job of making
their presence felt on Earth, which has turned the planet into an
archaeologist's playground.
Not content with stopping there, in
the last six decades we've blasted tens of thousands of objects into
space and given rise to a fertile new profession: space archaeology.
Australia's Dr Alice Gorman is a leader in the field and talks us through exactly what she does and why it's important.
She also has a warning for us mere Earthlings about what the future could hold if we don't change our ways.
How much stuff have we sent into space?
"We have currently orbiting the Earth at this point in time 23,000 bits of stuff over 10 centimetres in size.""So that includes whole satellites and fragments and bits that have broken off and rocket bodies.
"We have left a whole range of sites on the moon — we have the six Apollo landing sites, we have numerous Russian, Chinese, Indian and Japanese sites too.
"On Mars, there are rovers and orbiters and other kinds of vehicles. And then if you go further into the solar system, we have landing space probes on moons like Titan.
"We have the Voyager spacecraft right out at the very edge of our junction with interstellar space, and New Horizons, which is currently heading out in that direction, too.
"And lot more little bits of pieces in between. Really, the whole solar system now is a human artefact."
It sounds messy, but is this stuff dangerous?
"The stuff in Earth orbit is dangerous."We keep putting more stuff up there, it breaks apart and sometimes it explodes.
"Sometimes a country will fire a missile at a satellite and, as happened just last week with India, create a whole lot more junk.
Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume.
"So we are actually starting to create a bit of an environmental problem for ourselves."And also potentially down the track a problem where, if we launch anything into Earth orbit, it will be at a high risk of collision."
What's the oldest thing that's out there?
"The oldest object we have in space is a satellite called Vanguard 1, which was launched in 1958.""It is a beautiful little round, silver, aluminium, polished sphere with six antennas sticking out of it.
"If you look at pictures of it now, it is very sort of retro looking and has a vintage space-age look.
"I don't want to get my hands on it, actually. I want it to stay up there. Part of why it is so significant is the fact it is still in orbit.
"What I would like is some more data. I would like more people to be monitoring the condition of the satellite. I am happy for it to stay out of my reach.
"One day, maybe in 10, 20, 30 years as a space tourist, I would love to go and see this satellite in its natural setting."
Why is it important to collect, study and learn about it?
"This is really the history of the space age."This is now 60 years old, so people think it is very recent, even a little by futuristic. But, in fact, soon it will be 100 years since the first object was sent into space.
"We call it space junk, and junk is really what archaeologists study. We study the garbage left over by people in the course of their everyday lives, back millions of years.
"But this more recent stuff — while it has some hazards for space enterprises in Earth orbit — this is our heritage, too.
"Among those bits of junk are spacecraft that have incredible stories and, from my perspective, I want us to clean space junk up, but I don't want to do it at the expense of losing some of these amazing artefacts that have such unique stories."
How does a space archaeologist do their work?
"It is a bit ironic, isn't it? Field work is such an important part of archaeology, but if I had a spare few million dollars I could maybe go up on the International Space Station and do some firsthand observation myself."It is just not possible at the moment.
"So I use remote data. I use the big databases of all the objects launched into orbit.
"I read all the technical and scientific literature to work out how those materials survive and also to find out the stories about these spacecraft, to work out exactly in what ways they are culturally significant to us.
"So it is a lot of remote work."
How fast do these things deteriorate?
"This is something we don't have as much data about as we would like.
"We have to get that data from bits that come back usually, so we can see what happens to them.
"Space is a very dynamic place. It is full of radiation, micro meteorites, geomagnetic fields. And of course this has a big impact on how spacecraft function and how they survive.
"So it is something that we really need more information about.
"In general, the space environment is not kind to human materials."
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