at the Haleakala Observatory in Hawaii,

human beings detected the first-ever

visitor from interstellar space:

an object from outside our own solar system.

A pair of Harvard scientists say a massive,

fast-moving visitor to our solar system

may have been a probe

sent by an advanced alien civilization.

It's an alien spacecraft.

Some sort of alien technology,

perhaps exploring the cosmos.

It's called Oumuamua,

which roughly translates as messenger from the past

reaching out to us in Hawaiian.

Everything in our solar system is on a closed loop.

You know, some orbits are nearly circular,

some are elongated.

This one was an open-ended orbit,

which means it's coming from outside the solar system.

Then something even more strange happened.

Upon leaving the inner solar system,

astronomers reported an unexpected acceleration,

only adding to the hypothesis that Oumuamua

was some sort of alien creation.

It would be exciting to think this is an alien spacecraft.

You know, one of the burning questions on many minds is:

Are we alone?

But you have to be responsible about it.

And if there is a perfectly common explanation,

you shouldn't go to the exotic explanation.

After observing the object,

most astronomers agree that it's probably a comet.

Like 2I/Borisov,

the other interstellar object seen a year later.

But we may never know for sure.

Things that come in on these type

of very elongated orbits move really fast

when they're close to the sun,

and then they're much slower as they move out

of the solar system.

So when you looked at the brightness of this object,

it was going to only be easy to observe for about a week.

In that short window of time

with just a pinpoint of light,

scientists were able to make guesses on the object's shape,

its size, how fast it was spinning and its color,

which is thought to be reddish.

But there are a lot of questions about Oumuamua

and space that'll remain unanswered

unless we're able to act more quickly.

Right now, many of the teams are saying

we need the capability

to have reactive missions,

fast missions that can respond to a discovery.

Because right now, the missions,

the way NASA works with the small missions,

is you put in a proposal and it takes many years

to get that approved.

And then it might be a decade between proposal

and actually launching a mission.

And obviously for Oumuamua,

that would have been pointless.

So we would like to have missions that are maybe ready

to go, built and in orbit,

waiting for a new discovery

or something that could be launched immediately.

That's why teams of scientists

are planning missions to wait for objects in space,

and spring into action as soon as

something interesting is detected.

It may be humanity's only chance to see an object

from another solar system up close.

The space between solar systems is huge.

Unless warp drives become a reality,

traveling from one to another any time soon is

probably not possible.

Well, I mean, I'm a "Star Trek" fan,

and according to "Star Trek" in 2063,

I think, Zefram Cochrane invents the warp drive.

Zefram Cochrane?

Of Alpha Centuri?

The discoverer of the space warp?

That's right captain.

So if that happens, definitely.

If not, I think it's quite difficult

to reach anything within my lifetime.

Currently, the only way that we have to see

some of the material from these other star systems

is stuff that is in interstellar space that gets to us.

Although we've never gone near

an interstellar object,

we've learned a lot from approaching objects

from within our solar system.

In 2014, the European Space Agency's Rosetta probe

rendezvoused with Comet 67P.

Rosetta is the first mission

that ever delivered a lander to the surface of a comet.

This had never been done before.

It's the first mission that went into orbit

around a comet,

and it accompanied it for two years and a bit,

from 2014 to 2016.

And from this mission, the European Space Agency made a lot

of interesting observations.

I think this shape was one of the major surprises

that we had at the beginning.

No one really expected that.

Another really big discovery, I think, was that

the water that came off Comet 67P

is not that kind of water that we have on Earth.

And if it's not the same, you know that

they're probably not from the same source.

So I think this was quite unexpected

because people really thought

this comet could be a real possibility

to bring water to Earth.

Scientists are still looking at the data

from the Rosetta mission

and making exciting new discoveries about 67P.

And those discoveries in turn

give us hints about the early days of our solar system.

I think comets are very interesting

because they can actually tell us where we come from.

The comets are always thought as kind of

leftovers from the solar-system formation.

And if we explore comets,

we can understand how the solar system formed,

how Earth formed and basically

how humans in the end came to be

because without Earth we wouldn't be here.

While the Rosetta mission was a success,

Comet 67P orbits the sun every seven years

and is affected by the heat,

losing gases and changing its composition with each orbit.

Scientists at ESA recognized the need to study a comet

with a pristine surface,

one that's never been near the sun,

and that's largely unchanged

since the formation of our solar system.

This is known as a new comet.

They were talking about this problem

of pristine surface versus changed surface.

And they said, "Well, you know what we should do?

We should try and get to one of those new comets."

And so the Comet Interceptor idea was born.

This is very different from previous missions

that we've done where we've always gone to comets

that go round and round in the solar system.

And the reason why we go to these is that

we know where they are.

We can observe them and then get

their position very accurately.

But Comet Interceptor doesn't want to do that.

Comet Interceptor wants to go to a very new comet

and observe it with three different little spacecraft:

one mother spacecraft, as we call it,

and two sub-spacecraft.

And we want to basically observe everything we can.

We'll take pictures of the comet's nucleus,

which is a little thing in the middle.

We'll take pictures of the gases around it,

the dust that comes off of it, the environment.

Interstellar objects

are not Comet Interceptor's primary target.

Since we've only ever detected two,

we don't know when or if we'll detect another one.

This mission is mainly going after

unknown new comets from beyond Neptune in the Oort cloud.

This is the spherical, outer part of the solar system

and is believed to contain trillions of comets.

The majority have never entered the inner solar system.

But every once in a while,

one of these icy bodies gets a gravitational bump

from another object, flinging it

into the inner solar system.

And Comet Interceptor hopes to be ready for the next one.

And there is another very interesting target family,

let's say, which is interstellar objects.

So if there is an interstellar object

like Oumuamua or Borisov,

that's obviously where we we will be going

because that's by far the most interesting thing

that we can explore.

And Comet Interceptor is the only mission

that has the capability to explore

such an interstellar object.

But to catch up to a new comet

from our solar system or an interstellar object,

they needed to come up with a way to deal

with the short lead time,

something that's never been done before.

The problem is that

these dynamically new comets are usually detected

just a couple months before they get close to Earth.

And a couple months as everyone involved

in any space mission knows

is not enough to build a spacecraft

and go somewhere with it.

So we're actually more looking at a timeframe of five years

for the mission, where we have five years of waiting time

and we can choose whenever we detect a suitable comet.

And we think that the chance of detecting

a suitable, dynamically new comet

that we can reach is over 90% over these five years.

To be able to wait for a comet out in space

for up to five years, they'll send a small probe

to the Earth-Sun Lagrange point,

a place where the gravitational pull

from both bodies cancel each other out,

creating a stable orbit.

And when Comet Interceptor gets there,

it will just wait for five years.

And once we detect the comet we'll be

setting off towards rendezvous point,

and this will be done with chemical propulsion.

Data gathered by the interceptor

could be compared to other comet missions,

so scientists will be able to predict the effects

of the sun on comets,

giving them clues as to what the formation

of our solar system was like,

and in turn teach us about how Earth came to be.

It is a very ambitious mission.

That's, I think, why it's so exciting.

I mean, if you just do things that are easy,

it's a bit boring.

So this mission is very difficult to pull off.

And I think that

the team here at ESA has done a very good job

in kind of reminding everyone

of the constraints of the mission

while still getting the best science out of it

that we can expect at the end.

Although not as far along

as ESA's Comet Interceptor,

which is set to launch in 2029,

there is a team at MIT in its initial planning stages,

designing a mission specifically

targeting interstellar objects.

We see interstellar objects

as the new frontier in

planetary sciences.

And now that we detected them,

it really opens up the door of like, oh,

what new things can we discover?

And how do these new discoveries frame

our thinking about the formation of this star system

and other star systems?

So it's really science in a nutshell.

Their proposal is called

Dynamic Orbital Slingshot for Rendezvous

with Interstellar Objects.

Much like the Comet Interceptor,

it will wait in space and spring into action

at the right time.

So the unique part about our concept

is that using the solar sail,