The Solar System-4.
The biggest of all the Jovian storms raging at the moment is the Great Red Spot.
It is a gigantic storm 40000 kilometres long and 14000 kilometres wide.
This giant anticyclone has been raging for hundreds of years.
It is 3 times larger than the Earth.
It is thought that wind speeds reach over 400 kilometres per hour,
as this violent storm circles Jupiter every ten hours.
We don’t know why the storm has raged for so long, or what makes it so red.
It is thought that complex organic molecules formed from Jupiter’s upper atmosphere,
as it reacts with the Sun’s ultraviolet radiation, could be one factor behind its vivid colour.
Our moon is one of the 170 moons in the Solar System.
Our moon is the fifth biggest natural satellite in the Solar System.
It dominates our night sky because it is by far the biggest moon in the Solar System,
in relation to the size of its parent planet.
Our moon has a profound effect on the life of our planet.
It drives the ocean tides that are intimately linked to the cycles of nature.
It is even possible that tidal pools were the cradle for the origin of life on Earth.
Our moon is riddled with craters, the ancient remains of volcanoes, and atmosphere so tenuous,
that it is virtually indistinguishable from a vacuum.
The moons in the Solar System are an interesting, varied bunch of worlds.
One such place is Titan.
It is Saturn’s largest moon and the second largest moon in the Solar System.
It is bigger than the planet Mercury.
The Cassini spacecraft visited it, and its tiny sister, Huygens in 2004.
Surrounding Titan is an atmosphere that is 600 kilometres deep,
and 4 times as dense as that on Earth.
It is the most Earth like atmosphere we know in the Solar System.
It is a thick blue line rich in nitrogen, and some methane.
It is almost beyond imagination that a world this small,
should be able to hold on to such a dense atmosphere.
Mercury is too small and hot to hold on to its atmosphere.
Titan although larger in volume, is half the mass of Mercury,
and so has a even weaker grasp of the atmosphere surrounding it.
The reason why Titan has its wonderful atmosphere,
is because it lies in a much colder region of the Solar System, and that makes all the difference.
The temperature of a gas is essentially a measure of how fast molecules are moving around.
The higher the temperature, the faster they are moving.
The speed of the molecule is also related to the pressure the gas exerts.
Pressure is simply the effect of the molecules smashing against something.
The faster they are moving, the harder they smash into things, and the higher the pressure.
The ideal gas law states that pressure times the volume is proportional to the temperature.
PV = nRT.
P is the pressure, V is the volume, n is the number of molecules in moles, T is the temperature,
and R is the ideal gas constant.
It says if you keep the volume of the container fixed, and raise the temperature,
you have to raise the pressure, or lower the number of molecules, to keep the balance.
This concept is demonstrated by Chinese lanterns.
When you light up the fuel beneath the lantern, the air inside the lantern heats up.
The pressure inside the lantern begins to increase.
But the lantern is open at the bottom, and therefore the pressure inside the lantern,
must remain the same, as the pressure outside.
The pressure equalises by molecules of air rushing out of the bottom of the lantern,
that is decreasing in order to allow T to increase, and keep everything else the same.
The lantern weighs less and less as time goes by,
and eventually it is light enough to gently float into the sky.
Titan is one and half billion kilometres away from the Sun.
It barely feels the heat of the Sun.
From Titan the Sun is barely another star in the sky.
Titan is a very cold place.
Its atmospheric molecules are moving very slowly compared to Earth.
If it was as close to the Sun as Earth, it would not be able to hold on to its atmosphere.
If the Sun heated Titan to Earth like temperatures, its atmosphere would soon vanish.
However at 1.5 billion kilometres, the weakness of Titan’s gravitational pull,
is offset by the fact that its atmospheric molecules are moving around much slowly than in Earth.
This allows Titan to hold on to its atmosphere.
The astronomer Kuiper had incredibly acute eyesight.
It allowed him to see stars that were four times fainter than those visible to others.
The Kuiper Belt, the region of planetoids and asteroids beyond Neptune, is named after him.
Kuiper was the first to gather spectroscopic data,
that confirmed the presence of atmosphere on Titan.
Because of the thick cloud of gas shrouding Titan,
it was difficult to explore using telescopes from Earth.
The voyager space probe made the first detailed observations from nearby.
It took a mission of even greater audacity to reveal the world of Titan, beneath the haze.
In 1997, the Cassini space probe began its journey to Titan.
It carried with it the Huygens probe, which was designed to land on Titan.
In 2004, Huygens separated from Cassini, and navigated through its atmosphere.
The surface of Titan was revealed for the first time.
In the Huygen images you can clearly see rounded stones dotting the landscape.
It was similar to pebbles found on river beds on Earth.
Huygens seemed to have landed on a river bed,
providing evidence that there was rivers on the frozen moon, Titan.
This wasn’t the only surprise that Titan held in store.
Earth is just at the right temperature and pressure, to allow water to exists at the surface as a solid,
a liquid, and as a vapour in the clouds.
The Sun heats up the oceans, raises the water vapour above the surface as clouds,
moves it over the top of mountains, and returns it to the ground as rain.
The falling rain can then turn to solid ice, become a glacier, and sweep down the valley,
to sculpt astonishing landscapes, like the Alaskan Matanuska glacier.
Titan has the perfect temperature and pressure to allows something to exists as solid, liquid and gas.
This is very rare.
The Cassini spacecraft took radar images of the north pole of Titan.
They revealed that the surface was liquid.
These lakes cannot, of course, be lakes of liquid water,
because of surface temperature of Titan is minus 180degrees.
At these temperatures water is frozen as hard as rock.
If the lakes are not of water, what could it be?
Methane is common throughout the Solar System.
Here it exists as gas.
Lake Eyak is located in Alaska.
Methane bubbles up from the depths of Lake Eyak.
The floor of the Lake is covered in rotting vegetation.
The organic matter is broken down by bacteria,
and metabolic processes produce large quantities of this volatile gas.
Methane burns in the presence of oxygen, to produce water and carbon dioxide.
The earths temperature and atmospheric pressure means,
that methane can exist only as a highly flammable gas.
On Titan, the combination of temperature and atmospheric pressure,
allow methane to exists as a solid, liquid and gas.
The images Cassini captured, are gigantic lakes of liquid methane.
The largest methane lake in Titan is over 400,000 square kilometres.
It is five times the size of lakes Superior, America’s largest lake.
On Titan, methane plays exactly the same role, that water does on Earth.
Where we have clouds of water, Titan has clouds of methane, with methane rain.
Titan has lakes of liquid methane.
The Sun lifts the methane from the lakes and saturates the atmosphere with methane.
On Earth we have a hydrological cycle.
In Titan we have methanological cycle.
Methane rain in Titan turn into rivers, cutting deep into the frozen water ice landscape.
The atmosphere of Titan shaped the surface, just like our atmosphere shapes our surface.
Titan is like a primordial Earth, caught in a deep freeze.
Its water is frozen as hard as steel.
Methane flows as the liquid, like water does on Earth.
It is almost like looking back in time over 4 billion years and observing our planet.
This was before our atmosphere was changed by the delicate process of life,
into the oxygen rich canopy of vapours we see today.
We have now two Earth like worlds.
One is in a warm region 150 million kilometres from the Sun.
Another is in a deep freeze a billion kilometres from the Sun.
This greatly increases the probability that there are other Earth like planets in orbit,
around trillions of stars in the Universe.
The Grand Canyon is situated in the U.S.
It is estimated that the origins of this valley date back to 13 million years,
when the Colorado river began to carve its way through the rock.
This valley 466 kilometres long, 29 kilometres wide and 1.6 kilometres deep,
has been etched and carved by nothing more than the action of running water.
The extraordinary history of our planet is etched on the walls of this ravine.
From top to bottom, the layers of rock reveal a journey of 2 billion years of Earth’s history.
It displays evidence of rising sea levels and ice ages, ancients swamps and extinct volcanoes,
chronicle the ever changing life on our planet.
The walls of the canyon provide us with one of the most complete geological columns on Earth.
The planet is alive.
For billions of years it has been dynamic, changing and vibrant.
It is a world driven by intense heat at its core,
and shaped by the journey this heat takes to the surface and beyond.
The Valles Marinieris, in Mars is named after the space probe, Mariner 9 which discovered it.
It is 3000 kilometres long, 600 kilometres wide, and 8 kilometres deep.
It is so big that it could fit our Grand canyon in one of its side channel.
Launched in 1971, it was the first spacecraft to orbit another planet.
The images it sent back revealed many landscapes and features that we share with Mars.
Today we have more spacecraft orbiting Mars, and rovers on its surface,
which help us to understanding the geological evolution of the planet.
Mars has clouds which are believed to be composed entirely of water ice particles.
The landscape of Mars echoes many features found on Earth.
The Valles Marinieris is thought to be a tectonic crack that created it in the same way,
as the plate tectonics on Earth created the East African Rift.
We have also found evidence of landscapes formed by water courses, and permanent polar ice caps,
that ebb and flow with the seasons.
Despite the many similarities between Mars and Earth,
there are many differences between these two planets.
Mars is a cold planet.
It has an average temperature of minus 65 degrees.
It is also a planet with a tenuous atmosphere, compared to Earth.
Mars is now a dead and desolate wasteland.
The processes that sculpted its current landscapes seized up long ago.
There is no water to flow, and no active volcanoes.
As of now there is no evidence of life.
The laws of nature can play out, in radically different ways, in different planets.
Big Island is situated in Hawaii.
It is a part of an undersea mountain range that breaks through the Pacific Ocean,
to create a chain that runs over 2400 kilometres.
Everything on this magnificent island range is created by the intense heat,
that sits within the Earth’s core.
Although the Hawaiian islands are far from any tectonic plate boundary,
they are above a geological hotspot.
They are above a narrow stream of lava, that is thought to link it all the way,
to the boundary between the Earth’s mantle and its core.
As the Pacific Plate drifts over this hotspot,
it creates some of the most intense volcanic activity in the world.
The magma pushes through, it builds up over time to create the island volcano.
As the plate drift moves the volcano away from the hotspot,
the magma source is removed and eruptions cease.
The Big island is built from five shield volcanoes.
The most active of these is Kilauea, which means ‘spewing’.
It has been erupting almost continuously since 1983.
It is considered one of the most active volcanoes in the world.
Everyday you can see molten rock flowing down the side of the mountain,
destroying everything in its path.
Forests are turned into ash, and the pacific ocean boils as the lava hits the water and explodes.
Volcanic eruptions are Earth’s geological heartbeat.
The surface of our planet has been created and shaped by active volcanoes.
A few kilometres north of Kilauea is Mauna kea, which illustrates what volcanic action can produce,
given enough time.
Mauna Kea lies dormant today.
Its scale is testament to the enormous power that exists within the Earth.
Although this mountain is 4 kilometres above the surface of the pacific,
it is 10 kilometres above the surface of the pacific floor.
This makes it the highest mountain on Earth.
It is however tiny compared to the biggest volcano in the Solar System.
The Tharis region is located near the Martian equator.
This vast volcanic plateau is at the western end of Valles Marineris.
It is home to some of the biggest volcanoes in the Solar System.
One volcano dwarfs them all.
It is Olympus Mons.
It is a vast outpouring of lava which stretches over 600 kilometres.
It soars 25 kilometres into the Martian sky.
It is the highest mountain we have ever seen.
It was photographed by Mariner 9, in 1971.
Just like Mauna Kea, Olympus Mons is a shield volcano.
Over millions of years, layer upon layer of lava,
was built up during long periods of continuous eruptions,
slowly raising the mountain to truly gargantuan heights.
It is 550 kilometres in diameter.
It is so vast that standing on its foot hills, it is impossible to see its top.
It grew so tall because of the specific geology of Mars.
In Hawaii, a string of volcanoes is being produced as the Pacific Plate moves over a static hot spot.
As the plate drifts northwards over the hot spot, new volcanoes are formed.
Existing ones become extinct, as they are carried away from the source of heat.
On Mars, the lack of plate movement over the hotspot beneath Olympus Mons,
means that the lava has simply piled up.
Olympus Mons shares many of the features and qualities we find in shield volcanoes on Earth.
The geological processes that built them are identical.
Mars and Earth share more than geological similarities.
The origins of all the rocky inner planets - Mercury, Venus, Earth and Mars are very similar.
The story of their formation can be traced back to the birth of the Solar System.
The Sun had just ignited 4.6 billion years ago.
The infant Solar System was nothing more than a disc of dust and gas, orbiting the newly formed Sun.
This proto-planetary disc contained all the matter that would form,
the planets and moons of the Solar System.
This process took millions of years of slow construction.
The process by which the Solar System formed out of discs of gas and dust is not fully understood.
The most widely accepted explanation is known as the planetesimal theory.
Planets are born small, growing through gradual accumulation of dust and gas,
into larger and larger clumps.
Dust particles in the disc forms all clumps as they collide together randomly over millions of years.
Some accumulate more and more mass till they reach a critical size of about 1 kilometre.
These solid, ill defined objects are known as planetesimals.
After reaching this critical size, it is thought that mini planet sized objects grow very quickly,
because the growth rate increases as their mass increases.
This process is known as run away accretion and lasts only a few tens of thousands of years.
There are frequent collisions between the many proto-planets orbiting the young Sun.
Eventually through a process of continuing collisions and mergers,
a few Earth sized planets will be left.
Slowly, these newly formed balls of rock are transformed.
A combination of heat from multiple collisions,
plus the heat generated by the decay of radio active elements,
that were present in the proto-planetary disc, can melt whole areas deep inside the planets.
This allows gravity to take over,
so the heavy elements such as iron and many of the radio active nuclei, sink to the planet’s core.
Today on Earth, we can still see the remains of this primordial source of heat,
that has been trapped for billions of years, inside our planet’s core.
It is released through the eruption of volcanoes.
Earth’s volcanoes are driven by this ancient source of power.
So are the shifts in our tectonic plates that move whole continents, and raise great mountain ranges.
However, elsewhere in the Solar System this powerful source of energy ran out long ago.
The volcanoes of Mars are little more than a petrified memory of a distant, more active past.
For all its grandeur, Olympus Mons stands cold and extinct.
We can see no evidence of geological activity in Mars now.
As far as we know, Mars is now a dead World.
Its geological heartbeat has been extinguished.
Despite having the biggest volcanoes in the Solar System,
the primordial heat that form them is no longer beneath the Martian surface.
Something stopped Mars in its tracks.
Space is cold, very cold.
The temperature of the Universe is on average just over 2.72 degrees Kelvin,
which is minus 270 degrees celsius.
This is very close to absolute zero.
The fact that the Universe isn’t at zero degrees Kelvin is significant.
This precisely known number is the background radiation left over from the beginning of the Universe.
It is a fading echo of the Big Bang, 13.7 billion years ago.
In this freezing conditions, hotter objects including planets lose heat to space.
This is not lost by convection or conduction, since space is almost a vacuum.
Instead planets lose their heat through radiation, the emission of infrared light.
The overwhelming majority of this energy radiated into space,
is simply the energy a planet receives from the Sun.
If Earth didn’t re-radiate the Sun’s energy at the same rate at which it received it,
it would rapidly heat up.
Earth’s internal heat source plays an important role.
It is the primordial heat leftover from its formation,
and the radioactive decay of elements deep within its core.
The rate of loss of this heat is determined by the ratio of a planet’s surface area to its volume.
This is because the internal heat must be radiated out into space from its surface.
This is key to understanding why Mars is now geologically dead.
Mars is about half the diameter of Earth, and just 1/8th of its volume.
Volume is proportional to the cube of the diameter.
Mars would have stored less internal heat initially because it is smaller.
The critical factor is the surface area available to radiate the heat away.
Surface area is proportional to the square of the diameter.
So Mars has one quarter of the surface area of Earth, but only 1/8th of the volume.
This means it has more surface area in relation to the original heat store,
and so it lost its inner heat much faster.
The combination of these two factors defines the life of a planet.
Millions of years ago when the interior of Mars grew cold, the volcanoes lost their life blood.
The geological heart of the planet died, and its surface ground to a halt.
The fate of a whole planet was destined by the simplest laws of physics.
On Earth we have seen one beautiful manifestation of how simple laws of nature,
play out and build a planet.
On Mars we have another example of what happens when you take a planet smaller than Earth.
It loses its heat more quickly and becomes geological inactive.
These are just two examples of the delicately balanced processes that decide a planet’s fate.
We have also another nearby planetary experiment to explore.
There is a planet just like Earth, but its position closer to the Sun.
It is the brightest point of light in our night sky.
It is so similar to Earth that it has been called Earth’s twin.
However, Venus is a tortured world.
With an average surface temperature of 464 degrees,
it is the hottest surface on any place in the Solar System, other than the Sun.
Standing on Venus, we would not only be roasted,
but also crushed by the atmospheric pressure of over 90 times that of the Earth.
The clouds of sulphuric acid will threaten you with rain.
But it would never fall on you because the heat of the planet would evaporate it,
before it reaches the ground.
A couple of billion years ago, this hellish planet may not have been so inhospitable.
In its early history, Venus was probably not such a foreboding place.