Mercury and the Moon The Sky at Night

Good evening. For this programme,

we're going to talk about the strange little planet Mercury.

So first of all, over to Chris Lintott for a quick little run-down.

If you've ever seen Mercury, it's the most elusive of the bright planets,

because it stays so close the sun.

It does sometimes pop up in the evening sky,

but this month, it's a morning object.

'Mercury is the planet nearest the sun

'and it's a world of extreme temperatures.

'It's the smallest of the major planets

'and it has the oldest surface.

It has a large iron core,

which accounts for about two thirds of the planet's mass.

At a glance, it looks a lot like the moon, with craters and lava seas

but it's got a weak magnetic field and an extremely thin atmosphere

and these false colour images reveal a complex surface chemistry.

Although Mercury orbits the sun very quickly, it's turning very slowly,

so that one Mercurian day

lasts the equivalent of 176 Earth days.

The side facing the sun gets very hot, over 400 degrees Celsius,

while the side facing away from the sun gets icily cold,

minus 180 degrees.

It's a world of mysteries.

How did it form and why does it have this large iron core?

Mariner 10 was the first spacecraft to fly past Mercury

back in the '70s, but with the arrival of Messenger in 2011,

we finally had our first spacecraft in orbit.

Messenger has sent back stunning images,

like this one of the Coloris Basin,

the largest impact crater anywhere in the solar system.

It's also discovered volcanic vents and these strange hollows, or pits,

which give a Swiss cheese appearance

where materials vanished into space.

The poles of Mercury are also a mystery.

We've seen the signature of water

in the freezing, permanently-shadowed craters

at both the north and south poles.

For a planet so near the sun,

this certainly challenges our ideas about the solar system.

Katie Joy and Dave Rothery have come down to Selsey to talk to us

about some of these strange features that we see on Mercury.

Messenger has mapped the whole planet by now,

but it has still thrown up more questions than it has answers.

First of all, may I come to you, Katie?

What's the very latest news from Messenger?

Messenger has been in orbit about a year and a half now

around Mercury and we're finding out huge amounts of information

from all the experiments that are running on the spacecraft.

So lots of new things about Mercury and understanding the planet that is closest to the sun.

What about the Mercurian atmosphere?

Well, we've observations from Earth to suggest

that there are atoms around Mercury that form an exosphere,

so not necessarily an atmosphere, but an exosphere.

Some of the instruments on board the spacecraft are helping us

to understand the coupling of the exosphere

and the planetary surface in a bit more detail.

-The atmosphere of Mercury is very, very tenuous.

-Extremely tenuous.

It's great for remote sensing the planetary surface.

There's no air in the way, effectively.

These atoms are extremely diffuse, but they are there.

And what is recharging them is of considerable interest.

There are places on the surface which are quite remarkable which we didn't expect.

When we flew past Mercury, we saw craters

with bright patches on the floor.

I remember discussing them with you, Patrick.

We were scratching our heads - what are these craters or bright patches?

Now we are in orbit around Mercury, we see hollows on the surface,

we see something is removing the surface, we don't know how.

The only thing we can think of is that the surface material is somehow disappearing into space.

Maybe it's subliming, turning from solid to vapour.

It's a really strange landform

and this is one way we can get these atoms into the exosphere.

One point here, people compare Mercury with the moon.

In some stages, it's like the moon, in others, it's totally unlike.

It is, it's very different. We have the heavily-cratered areas

which suggest Mercury has been bombarded by very large asteroids and comets throughout its history.

We think most of those basins, which are over 300 kilometres

in diameter, were probably formed very early on in Mercury's history.

So prior to about 3.8 billion years ago.

And then subsequently we've had vulcanism which has

erupted in different areas on the surface of Mercury

and flooded very thick lavas into those ancient basins.

And Messenger is taking images of the surface in new detail

so that we can study some of these volcanic sites.

We hear about water holes on Mercury. I'm a total sceptic.

-What about you, Chris?

-No, I think some of the evidence is convincing.

The first signs of what might be water were seen with radar.

Yes, you can image parts of Mercury with radar from the Earth,

and resolve individual craters

and within some of the polar craters, at both poles,

there was something which was sending back a strong radar return.

So you've got a strong bounce.

Something's scattered back strongly by something

which has properties which could be water ice, could be sulphur.

Mixed up with the soil as well.

We're not talking about an ice rink that you can skate on.

No, I think in terms of small crystals within the soil.

Water or sulphur are the obvious ones to give this kind of radar return.

We now know that these are areas on Mercury

where parts of crater floors are in permanent shadow.

They're so close to the poles, the sun never appears on the crater floor,

so it's very cold all the time.

Never gets above about minus 170 centigrade, something like that.

A similar effect on the moon.

So again, we have evidence from radar scattering

of some of these permanently-shadowed craters at the south pole of the moon

that they could have some of this water-ice properties.

I'm a total sceptic. When someone gives me a cup full of lunar water,

then I'll admit I was wrong.

-That'll be a very expensive drink, Patrick.

-Very.

-Well, Dave, Katie, thank you very much.

-Thank you.

As we've heard, Patrick, Mercury has many mysteries

and the next spacecraft to try and unravel them is a European one called BepiColombo.

And that spacecraft is currently in Stevenage, being assembled,

and Chris North went to take a look.

Astrium have been building satellites in Stevenage for over 40 years.

Walking the long corridors with Jessica Marshall,

a spacecraft and satellite engineer, I'm reminded how far we've come

since 1957 when Sputnik was launched into space.

In the Andromeda lab, there are three satellites under construction.

This communication satellite will eventually circle the Earth

tens of thousands of miles up, beaming down digital television signals.

It has the latest satellite technology

and we've been asked not to film any details which competitors might see.

It's a small world, with closely-guarded secrets.

But we're here to see this satellite, called BepiColombo,

which will eventually circle the least understood of the planets in the solar system, Mercury.

It's named after the scientist who worked out the best way

of getting a spacecraft to this tiny world.

The scientific instruments which will tell us about Mercury's atmosphere,

what the planet is made of and how it was formed will be fitted onto

this structure, the middle section of a three-part satellite.

Behind us we've got BepiColombo or part of BepiColombo.

Tell us what we've got here.

This is the very middle part of BepiColombo, the planetary orbiter.

It's going to be the European scientific module,

so all the science instruments will be mounted onto this

and this will be in orbit looking down at the planet.

But what you see here is only a third of that,

so the whole thing will be about the size of a bus.

On one side will be the transfer module to get the whole stack to Mercury.

And on the other side will be another spacecraft

which will be looking at the magnetic field around the planet.

Jessica is part of a team spread across Europe and Japan,

which is getting BepiColombo ready for its long journey

under harsh conditions around the first rock from the sun,

where temperatures will reach 350 degrees Celsius.

Because we're so close to the sun

and because we're going to heat up so much, we have to be very accurate

to make sure the long bits don't point at the sun,

so the scientific instruments, we can't point them at the sun.

We have to make sure we are controlling the spacecraft properly.

But also, there's a six-year journey to get there,

in itself a big engineering challenge.

So all these modules are stacked together

and then spend six years going towards the planet.

Then, after six years, we have to separate them.

That's a big challenge because if it doesn't work

then that's going to have huge implications on the mission.

Today, the engineers are welding together the fuel pipes

and putting in valves for the thrusters that will control BepiColombo

when it gets to Mercury.

Unlike its conventional neighbours with their big fuel tanks,

BepiColombo will be travelling most of the way by ion propulsion.

This is one of the tanks that will contain xenon gas.

Not your conventional rocket fuel, but for BepiColombo,

it's crucial to its novel ion propulsion engine.

But when it gets to Mercury, it's key to slowing the spacecraft down

and letting it get into orbit around the tiny planet.

Ion propulsion might sound and look like science fiction,

but while it is a relatively new technology,

it has been well tested on previous space missions.

Once in space, BepiColombo's engines will use a steady stream

of tiny charged particles of ionised gas to push the spacecraft along.

The ion thrusters are being developed in the UK too.

This footage from QinetiQ in Farnborough

shows the distinctive blue plasma produced by ion engines.

And while the frost produced is relatively tiny,

ion engines are incredibly efficient

and can continue to fire for very long periods of time.

They are ideal for a journey that will take more than six years

and cover several billion miles.

And there's one more key difference.

For most of the journey, BepiColombo's engines will be acting

like a brake, counteracting the sun's incredible gravitational pull.

In order to get to Mercury, you have to slow down.

So you've got to spiral in towards the sun.

And that takes quite a lot of energy to do.

It takes more energy to do that than to get us out to Jupiter or Saturn.

And that orbit uses the moon, the Earth and Venus

to do gravity-assist manoeuvres and to slow us down.

So it's like the slingshots that we think of

to get out to the distant reaches of the solar system,

-but actually slowing you down rather than speeding you up.

-Exactly.

And it means that we are able to get to Mercury in the most fuel efficient way.

We've got to make it as light as possible

because if we make it too heavy, we won't be able to launch it,

but also we won't be able to get it to Mercury.

And we want to get to Mercury and do as much science there,

and the more mass we save on the structure and propulsion means,

the more mass we can give to the scientists

and they can have bigger and better instruments on board.

Bepi is currently being spun around to allow closer inspection.

The Astrium engineers are very careful and rigorous.

Bolts are tightened and everything is checked and rechecked.

But it's still a tense time.

A few years ago, an American company wasn't as careful and dropped

a NASA satellite during a similar procedure.

Oops!

Finally, Bepi is turned over to reveal its huge radiator panel,

which will help cool its science instruments

and allow the engineers to start work on the next section.

Of course, when it gets to launch,

it's going to get a far less gentle treatment.

And lift-off of Messenger on NASA's mission to Mercury.

With the launch, it's the worst-case environment for a spacecraft.

So you think about it being at the top of that rocket and the rocket's lit

and it begins to accelerate out of the Earth's environment.

It's shaking around, but there is also a big acoustic noise,

big shock waves, which will go through that whole spacecraft.

So on Ariane 5, when you release the side boosters,

big shock waves going through the spacecraft.

We have to make sure we survive that.

Launch is on schedule for 2015. Not long to get Bepi ready.

It's a long time in the planning and will take a long time to get there.

But once at Mercury, BepiColombo should solve

many of the mysteries that Messenger has uncovered.

In the meantime, images of Mercury, never before seen,

are being sent back all the time.

But you don't need a multi-million pound spacecraft

or ion propulsion to get you out of bed in order to appreciate Mercury.

This month, it'll be on view from Earth in the early morning,

just before sunrise.

Back to Patrick's garden, where Pete and Paul can tell us more.

Pete, here we are and we have a nice little planet in the morning sky,

-the planet Mercury which I've only ever seen once.

-Have you really?

-Yes.

Well, this is a good opportunity to see Mercury

because it's in the morning sky,

visible just before the sun comes up.

It's actually joined by two other planets - Venus and Saturn.

And it's Venus that's really the key to finding Mercury.

Venus is moving between Saturn and Mercury

over the first couple of weeks of December.

But the morning I'd really recommend

is 11th December

because there's a fantastic little crescent moon there as well

which joins the party. That really sets things off.

Mercury is the lowest of the dots

and it's fainter than Venus,

-but it's still quite bright.

-It's also one of those things

that it's nice to say you've seen it. Also, we have in December

the Geminid meteor shower. This will be a good one this year, won't it?

I'm really looking forward to this because...

-The moon is out of the way.

-It's new, the moon, on 13th December.

That's when the peak of the Geminids is.

So what you have to do on 13th December, you must do this,

is get yourself a sunbed or a sun lounger,

-star lounger, shall we call it?

-Star lounger!

And lie outside just before midnight through to dawn,

that's the best time,

and you should get a fantastic view of the Geminid meteor shower.

The peak rate is about 100 plus meteors per hour.

I'll find somewhere dark away from the city, because I want to see some bright ones myself.

To be honest, we've had a very poor period of weather,

so I'm going to look for some clear skies in the country.

-I'm just going to drive to them.

-You can pick me up on the way!

-I'll come with you. Well, all these things present lovely photo opportunities.

-They do.

People should go to our Flickr site.

There also, we will find the observing guides,

-written by your good self, for the Moore Winter Marathon.

-Absolutely.

That brings us on to our next bit, which is binocular objects.

We have a nice collection of binoculars here.

We should start off by talking a bit about binoculars.

They're really just two telescopes coupled together.

Yes, and some of the objects we picked for the Moore Winter Marathons

are designed to be viewed with just binoculars.

We have 8x30, and the ones I started with 10x50, all the way to 11x80.

Yes, but you don't have to spend a fortune to get a decent pair.

The size which you would normally recommend for astronomy

would be either 7x50s or 10x50s.

Those numbers, let me explain what they mean.

With a 10x50 pair of binoculars, that's 10 times magnification

and 50 millimetres diameter front lens, basically.

So these 11x80s will magnify 11 times

and they have 80 millimetre lens.

Which is quite big, it's over three inches.

It is, but that's a problem with bigger binoculars

because to hold them steady, you really have to have arms like Popeye to keep them still.

There's that problem, which is an issue.

These are actually 15x70,

so that's quite a high magnification, 15,

so I've got them on a tripod here and that steadies the binoculars.

It's a good solution. You do have a cheaper method, though, don't you?

You can use a broom.

I would not recommend that to anybody, because I tried it once

and all of God's creatures, the spiders and slugs, all dropped out.

Basically, you take the broom and invert it, so you put the binoculars

-on the bristles and that helps you steady them as you look.

-Absolutely.

Let's talk about some of the objects in the Moore Winter Marathon

which we can see with binoculars.

Let's start with M33, the Triangulum galaxy.

This is a spiral galaxy, one of the members of the local group

which comprises our galaxy, the Andromeda spiral, a couple of others.

It is an interesting object, but has a very low surface brightness,

so quite a hard object.

You can see it with the naked eye if you've got really good skies,

but the way to guarantee a view is not to use a telescope

because that's got too much magnification,

it's to use a wide-field instrument, like binoculars,

because it gives you a nice wide part of the sky to look at,

collecting all that delicate light you've got.

That's come from nearly 3,000,000 light years away.

Interestingly, the way to find it,

you normally use the Great Square of Pegasus to find the Andromeda galaxy.

So if you start in the bottom right of the Great Square of Pegasus,

so the one in the upper left,

keep that line going

until you come to a star

of similar brightness.

Then, if you turn at right angles

to that, going up the sky,

you get to a fainter star,

then a fainter star still

next to that.

The Andromeda galaxy is the faint,

elongated smudge next to that star.

-Right.

-Which, with clear, dark skies,

isn't too difficult to see.

If you then draw a line from the Andromeda galaxy to Mirach

-and keep going for the same distance again...

-Goodness me.

It's just as well this is in your observing guide, honestly.

If you draw a line from the Andromeda galaxy

through the main star...

I'm completely lost.

Does this ever have an end?

And go other way for the same distance, that point exactly at M33.

Let's go from something

which is outside of our own galaxy

to something which is inside our own galaxy

-and that's the Beehive Cluster. M44.

-This is a lovely thing.

It's one of those objects, I'm glad you put it in the binoculars,

-because a telescope just does not do it justice.

-Too much power.

Too much power. You really want a low-field small pair of binoculars

and you get all these beautiful stars in this cluster.

I'm not a big fan of open clusters,

but the Praesepe is a really good one.

Quite interestingly, recently, we know some of the stars

within that cluster now hold extra solar planets

so it's a cluster of interest at the moment.

There's another really nice cluster -

-I'm annoying you here, aren't I, with clusters?

-No, it's fine.

I know you only put them in to annoy me.

If you find Orion the Hunter, which is very easy,

you can't miss it,

you find the three stars which make the belt of Orion,

and you follow them down to the left, they point to Sirius,

the brightest star in the night sky.

Well, just below Sirius, if you look at that region

with a pile of binoculars, there's a lovely cluster known as Messier 41.

Moving away from clusters now,

there is a lovely thing that you put on the list,

and I think this is probably

one of the most beautiful things out of the whole thing,

-and that's Kemble's Cascade.

-Ah, yes.

I've seen a few pictures on our Flickr site,

so quite a few people have commented.

This really is one of those undiscovered objects,

so easy to find, and yet it's so rewarding when you do find it.

You just don't think to look for it.

It's in the constellation of Camelopardalis,

which is very obscure and it's quite difficult to navigate around it.

-But I can give you a trick to find it.

-Go on, then.

If you have the W of Cassiopeia

and you join one end of the W to the other towards the left,

if you extend that link the same distance again,

that points exactly at Kemble's Cascade.

-Yeah.

-And that makes it very easy to locate.

People can go and find them

by using the Moore Winter Marathon guide and observing forms

which are available via the BBC's Sky At Night website.

Well, some lovely things to look for in the winter marathon,

all we need is the skies to clear. Did you know that this is actually

the 40th anniversary of the Apollo 17 mission?

So here's Chris Lintott to look at some of the highlights

of our last manned expedition to the moon.

10, 9, 8, 7. Ignition sequence.

Started, all engines are started.

We have ignition. 2, 1, 0.

We have a lift-off.

We have a lift-off and it's lighting up the area.

It's just like daylight here at the Kennedy Space Center.

The Saturn V is moving off the pad.

In December 1972, Apollo 17 left for the moon.

It was the only night-time launch of a Saturn V rocket

and a spectacular and dramatic sight.

Its crew, Ron Evans, geologist Harrison Schmitt,

and the last man to stand on the moon, Commander Eugene Cernan.

RADIO: We've got a beautiful picture, you guys down there.

Apollo 17 landed in the Littrow Valley,

amongst a range of mountains formed by a huge and ancient impact.

It made an ideal site for geological investigation,

with layers of ancient bedrock and new volcanic deposits.

The astronauts spent three days in all - collecting samples,

setting up science experiments and just occasionally having fun.

# I was strolling on the moon one day... #

ALL SING

May! May!

Commander Eugene Cernan was an experienced Navy pilot.

He first flew into space with Gemini 9, Apollo's predecessor,

and then again with Apollo 10.

In 1982, Patrick interviewed him for The Sky At Night.

Recently, I went back to Texas to talk to the last man on the moon.

What about navigational problems. Did you have any?

We studied, due to a great deal of your work, of course,

on the mapping of the moon, we studied the area

we were going to land so well that I really believe I knew it,

at least from the air, from above, as well as my own backyard.

But it's hard for me to realise

that I literally have been on another planet.

The Littrow Valley did not disappoint.

With its dramatic scenery and incredible boulders, the astronauts

were kept very busy gathering bore samples and bits of rock.

The discovery of orange soil at Shorty Crater

was unexpected and exciting.

Hey! There is orange soil!

Well, don't move it till I see it.

I've put my visor up. It's still orange!

Fantastic, sports fans.

The orange soil samples were returned to Earth.

High in zinc, these glass beads

are now thought to have formed in volcanic vents.

Can you see this on your colour television? I'll bet you.

How can there be orange soil on the moon?

Eventually, the incredible adventure on the moon was over

and the astronauts had to go home.

It ended a remarkable chapter in the history of exploration.

You were the last man on the moon.

What were your overall impressions of the moon?

My overall impressions of the moon are really...

overshadowed by my impressions of looking back at the Earth.

The moon itself, it's been called like a sandy beach,

it's colourless, but it is beautiful. It's majestic.

It's got towering mountains

and it's got a tremendously overpowering landscape.

What a nice day.

There's not cloud a in the sky.

3, 2, 1. Ignition.

We're on our way, Houston.

The legacy of Apollo 17 still lives on.

NASA's lunar reconnaissance orbiter is currently mapping the moon,

and it recently imaged the Apollo 17 landing site.

You can clearly see the lunar module, the buggy tracks

and even those of the astronauts themselves,

just as fresh as they were back in December 1972.

With no weathering on the moon, time seemingly stands still.

Back on Earth, the samples the astronauts returned

are still telling us new things

about the moon, our celestial neighbour.

Katie Joy has been lucky enough

to work with some of these precious relics.

Apollo 17 went to a very special place on the moon,

probably the most interesting of the Apollo sites.

So why there? What was interesting?

They went to the rim of the Serenitatis impact basin,

one of these really large impact basins on the near side of the moon.

And this is the boundary between the edge of that basin

and the surrounding highland areas, where there is a steep valley,

the Littrow Valley, which has been subsequently flooded with lavas,

so this was a geologically diverse site.

It had both highland rocks

so we could look at the ancient materials on the moon

and also the much younger lavas.

So it was to provide as much diversity as possible

to try and understand the geological history of the moon.

The sea area there was absolutely magnificent.

They brought back 110kg of moon rock,

and this is far more than all the other Apollo missions.

We had the deep drill core on Apollo 17 where they brought up material

from three metres in depth below the lunar soil,

so the lunar regolith, material that covers the surface of the moon,

and so this deep drill core provided us

with a snapshot back in time through what material was formed

at different points in the past.

So that's been really important.

But having a scientist there, a geologist, to know where to go,

I think helped a lot particularly for this latter mission.

18, 19 and 20 would have been geologists. Sadly, they never went.

No, the three latter missions that were planned but never went.

But maybe in the future when we go back

and explore the surfaces of other planets there will be

more scientists that will have the opportunity to interact

and sample the surface.

Well, I volunteer, for starters. If you need an astronomer.

I would love to have gone to a newer planet. No chance.

What would you say are the real scientific legacies

of the Apollo missions? Not just Apollo 17, but as a whole?

Many of the samples are still being studied in laboratories

around the Earth, so as technology has increased in the past 40 years

we can study smaller and smaller amounts

and find out new types of information.

One of the really interesting things that's come out of the orange soils

that Apollo 17 sampled

was the identification that they were rich in water,

suggesting the lunar material is actually relatively

a lot wetter than we thought it was,

which helps us to understand the internal structure of the moon

and where these sorts of volatiles come from.

And that's only been rediscovered within the last five years or so.

But we also placed a series of experiments on the surface

so the ALSEP packages which are in-situ experiments

that were left on the surface of the moon to conduct science

and that lasted after the astronauts left,

so we have seismic information which provides us about the variation.

-Looking for moonquakes.

-Moonquakes, exactly. From this particular site.

But also understanding the local heat flow,

the thermal environment of the moon, and placing these retro reflectors

where we shine lasers up from Earth

to understand how the moon is moving away from us as well.

So lots of good geology from rocks

but lots of good surface science experiments as well.

Well, Katie, thank you very much indeed.

When we return this rock or some of the others like it to Houston,

we'd like to share a piece of this rock with

so many other countries throughout the world.

We hope that this will be a symbol of what our feelings are,

what the feelings of the Apollo programme are,

and a symbol of mankind that we can live

in peace and harmony in the future.

Patrick, one more thing we have to talk about before we go.

There was a total eclipse of the sun from Australia a few weeks ago.

Beautifully clear over most of the eclipse, some great photos,

including this video sequence I've been sent showing the sequences

of the eclipse and totality itself,

with the pearly-white corona, the sun's outer atmosphere

shining out in what looks like a glorious eclipse.

-Don't you wish we'd been there?

-I wish we had.

-Next time.

Have you got a new telescope, or are you going to get one for Christmas?

Next month I'll be giving you a few tips about how to set it up

and how to use it. Until then, good night.

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