The Solar System-5.
The Deccan Traps in India is a rich landscape which extends to over 500,000 square kilometres.
Hidden beneath the green landscape, is a secret that holds a tantalising clue,
to understanding how Venus choked to death.
The Deccan Traps is one of the largest volcanic features on Earth.
65 million years ago, this area witnessed a series of colossal eruptions, that lasted 30,000 years.
At one point an area the size of half of modern India was covered by lava.
It covered an area of 1.5 million square kilometres.
The impact on the Earth’s climate was equally enormous.
Millions of tons of volcanic ash and gases were hurled into the atmosphere,
with a devastating effect on life.
These eruptions affected the climate so profoundly,
that it is possible they played a role in the extinction events,
at the end of the Cretaceous period that wiped out 2/3rds of the species on Earth.
This place was created from one of the most sustained and violent events of our planet.
The formation of this landscape is echoed on the surface of Venus.
The thick layer of opaque clouds that surrounds Venus,
severely limited our knowledge of the surface of Venus.
In 1990, Magellan arrived in Venus, and peered through the clouds with radar mapping.
Magellan saw a world of volcanic destruction beyond anything seen on Earth.
It is a landscape built on exactly the same geological foundations as the Deccan Traps,
but on a far larger scale.
We have discovered over thousand six hundred volcanoes on Venus.
It is far more than any other planet in the Solar System.
85% of the planet is covered by basalt lava plains, that have poured across the surface.
It is not known for certain if Venus is still volcanically active.
Because it is similar to Earth’s size, it might be expected to have a hot geological heart,
powering its volcanoes.
In 2010, the ESA spacecraft Venus Express provided evidence of volcanic activity,
as recently as 2.5 million years ago.
Many of the volcanoes on Venus are identical to the ones on Earth.
Shield volcanoes like Maat Mons litter the surface.
Although the underlying geology is the same, the character of these volcanoes can be very different.
On Earth shield volcanoes like Mouna Kea and Hawaiian volcanoes can be up to 10 kilometres high,
but much wider.
On Venus some volcanoes have footprints of hundreds of square kilometres,
but average heights of only 1.5 kilometres.
The Venusian volcano Sif Mons is a massive 300 kilometre across, but only 2 kilometres high.
Venus also has a type of volcano called tick volcanoes, that does not exists on Earth.
They are remains of volcanic domes that have collapsed.
It also has thousands of strange flat volcanoes that are called pancake domes.
They are clustered in groups across the Venusian surface, and are much wider than those on Earth.
Venus is a world dominated by volcanoes, but unlike on Earth,
this intense geological activity pushed our cosmic twin, down a path of no return.
Four billion years ago it is thought that Venus was a world much like our own.
The climate was cooler, and the surface may have been covered in vast oceans of water.
Just like Earth, this wet warm environment may have been the perfect place to harbour life.
How long these conditions existed is still unknown.
There is evidence that Venus was a more welcoming place for 2 billion years.
If this was the case, many scientists believe that Venus could have been the most likely place,
for life to evolve, other than Earth.
If the conditions were stable enough for a few hundred million years,
then life may even have flourished before the character of the planet turned ugly.
This is one reason why understanding the history of Venus is so important.
The hellish world provides the most telling example of the potential fragility of planetary environment.
Explaining why Venus and Earth reacted so differently to the same kind of volcanic cataclysm,
requires an understanding of a matrix of different factors.
Volcanoes don’t just produce heat and lava.
They produce vast amounts of carbon dioxide.
Every planet, including Earth absorbs energy from the Sun as visible light.
This light streams through the atmosphere almost untouched and is absorbed by the ground,
heating it up day after day.
The ground then reradiates this energy as infrared radiation.
Atmospheric gases, particularly carbon dioxide, are very good at absorbing infrared light.
They trap the heat and the planet heats up.
The more greenhouse gases in the atmosphere, the more a planet will heat up.
On Earth we are beginning to see the effect that an increase in the greenhouse gases,
created from the burning of fossil fuels has created.
Global warming is a recent phrase.
It would have wreaked havoc on our planet long ago,
if it hadn’t been for a familiar characteristic of our weather.
One of the most important reasons that Earth has taken different path from Venus,
is something we take for granted.
Rain plays a significant role in keeping our planet a pleasant place to live.
It acts as a part of a global recycling system.
It keeps our atmosphere in balance by washing out potent greenhouse gases like carbon dioxide,
and locking them again in rocks and oceans.
On Venus the planet’s position in the Solar System, combined with the laws of physics,
have conspired to make it impossible for rainfall to cleanse the atmosphere.
Venus, because it is slightly closer to the Sun, is a little hotter than Earth.
Venus lost all its liquid water.
The oceans of Venus would have gradually evaporated into the atmosphere, and escaped into space.
With no water, there is no rain on Venus.
So for billions of years there has been nothing to temper the buildup of volcanic gases,
in the atmosphere.
Venus ended up cocooned in a thick, dense, high pressure blanket of green house gases.
It made the temperature rise inexorably, and turn Venus into the hell like world we see today.
Compared to scorched Venus and frozen Mars, our planet is a very special place.
Although governed by the same universal laws, the Earth is not too big,
too small, not too hot and not too cold.
That is why the Earth is called the Goldilocks planet, because everything seems just right.
But the life and death on our planet is influenced by more than just the forces,
emanating from the depths of our world.
Our fate is intimately connected with our cosmic neighbours in ways that are subtle and complicated,
but extremely powerful.
Jupiter, king of the Gods, the fifth planet from the Sun, has been revered since the ancient times.
It is visible to the naked eye in the night sky.
It can also be seen during the day when the Sun is low on the horizon.
For millennia humans have imbued Jupiter with power.
From the Romans to the Greeks, the Chinese to the Hindus,
almost every civilisation has gazed at its light, without realising the true influence it exerts,
over our Solar System.
Jupiter by far is the largest planet.
It is so big that it could fit thousand Earths.
It is one of the four gas giants that orbit the Sun.
Along with Saturn, Uranus and Neptune, it is made up of the same substances as a star,
hydrogen and helium, the most common elements in the Universe.
Although it might have a solid core made up of heavier elements, Jupiter like all the gas giants,
is an ethereal planet.
It is a planet with more real boundaries in its skies, and no substances further down.
It is a vast atmosphere that gets denser and denser, as you travel deeper.
Jupiter has a mass that is two and half times as that of all the other planets put together.
It is so big, theoretical models suggest that if it was any more massive,
it would begin to collapse under its own gravity,
transforming it into a sub-star-like object called a Brown dwarf.
Jupiter is probably about as big as a planet of its composition and construction can be.
It dominates the rest of the Solar System.
Jupiter influences our planet Earth, across half a billion kilometres of space,
through the force of nature that binds the galaxy together.
Gravity is one of the four fundamental forces of nature.
It shapes so much of our Universe, and yet it is by far the weakest force.
Gravity has two properties that allow it to shape our Universe.
Everything that has mass or energy attracts everything else.
If you add more mass to something the gravitational force between it and other objects increases.
It also has an infinite range.
This means that its influence can stretch across the Solar System and beyond.
The force of gravity is directly related to the mass of an object.
Because it is the most massive planet, Jupiter has the most powerful gravitational field,
in the Solar System, other than that of the Sun.
Jupiter’s gravitational pull is strong enough to profoundly influence the orbits,
of passing inter planetary asteroids, and other wandering space debris,
even at large distances away.
The effect on the wandering objects can play out in three different ways.
Firstly, Jupiter can capture it.
Second, it can change its orbit around the Sun,
in such a way that it throws it out of the Solar System forever.
In the third case, if the angles are just right,
the planet can deflect an orbiting asteroid into a new orbit.
Occasionally this may place the asteroid into a collision course with a rocky inner planet,
including our Earth.
The PS-1 observatory is located on top of the mountain,
Heleakala on the Hawaiian honeymoon island of Maui.
It contains some of the largest digital cameras ever built.
It is designed to capture images with a staggering 1400 mega pixels,
on a area of 40 square centimetres.
Its objective is to trace asteroids which are potentially dangerous to Earth.
If anything bigger than the kilometre in size hits the Earth,
it would probably kill almost everyone on Earth.
Most of the known asteroids orbit in the asteroid belt, between Mars and Jupiter.
200 of these asteroids are known to be larger than 100 kilometres across.
A few million are bigger than a kilometre.
This sounds like a lot, but in fact the asteroid belt is mostly empty.
No spacecraft we have sent through it, has ever encountered a problem.
One of the objects in this region is Ceres.
It was once thought to be a planet, but now classified as an asteroid.
The name asteroid was coined by William Herschel, and means star-like.
In 1991, we got close enough to the asteroid belt,
with the Galileo spacecraft to take an intimate view at one of these mini worlds.
The orbit of most of the millions of asteroids don’t pose any threat to Earth.
We currently know about 7000 near-Earth asteroids.
Nearly a thousand of these are bigger than 1km.
Some of them could be of concern to Earth.
This is because of the influence of Jupiter on these asteroids.
The PS-1 observatory is specially designed to spot any moving objects like asteroids,
so as to identify any potential threat to Earth.
In 1970, a crater over 180 kilometres wide was discovered in Mexico.
Evidence suggested that a catastrophic impact had created this crater.
It is now called the Chicxulub crater.
It is one of the largest known impact craters on Earth.
It is estimated that the object that struck was at least 10 kilometres across.
This asteroid is thought to have struck 65 million years ago, at the end of Cretaceous period.
It coincides with the most famous extinction event in the history of the planet.
This event caused the disappearance of dinosaurs.
Many scientists think that the Chicxulub impact was the trigger for the extinction of dinosaurs.
This asteroid’s journey to Earth was influenced by Jupiter’s gravity.
There are many smaller impact sites on Earth, and many more which have dissolved over the years.
The asteroid belt is a vast expanse of space extending over 240 million kilometres,
between Mars and Jupiter.
This is further than the distance from the Earth to the Sun.
Now and again, because of the collisions in the asteroid belt,
a stray asteroid will get thrown into a position where it periodically aligns with Jupiter,
over and over again, and settles into a rhythm known as orbital resonance.
Jupiter is such a massive planet that it will give such an asteroid a gravitational kick,
changing its orbit.
Over time these orbits can get elongated and elliptical rather than circular.
This means they can get thrown into the inner Solar System, and cross the orbits of the inner planets, including Earth.
The surprising thing about these catastrophic asteroid impacts,
is that they may actually have been instrumental in shaping our planet,
and the life that flourished on it.
Impacts have been one of the driving forces of evolution on Earth.
It changed the climate and triggered extinctions, when huge swathes of life on Earth are wiped out.
It created the ecological niches, into which other species like ourselves evolved.
It is incredible that a planet half a billion kilometres away, could dictate our fate,
and define the life and death of a whole world.
The Quiantang river in China is famous as a location of the world’s largest tidal bore.
It is a phenomenon that creates a wall of water 50 metres high, travelling at 40 kilometres per hour.
Tidal bores occur in a handful of places, as they need both a particular shape of a river system,
and a large tidal range.
Across our planet tides rise and fall every 12 hours and 25 minutes.
They are the most visible mark of the most intimate interaction we have with any celestial body.
Tides are the direct effect of the moon on the body of water that covers our planet.
On one side of the planet the high tide occurs at the point on Earth,
where the ocean is closest to the moon, and so the gravitational force is at its strongest,
pulling the water towards it.
12 hours later and the same location will be at the furthest point from the moon.
So the gravitational pull on the water in the ocean is at its weakest.
At this point the Earth is pulled towards the moon slightly more than the water,
and there is high tide at that point.
The Sun can also affect the tides on Earth through the same gravitational effect.
Even though the Sun is significantly more massive than the Moon,
it is further away so the effect is much weaker.
It is the moon that most powerfully drives this bi-daily rise and fall of the oceans.
We have been studying the tides and plotting their rhythms for thousands of years,
unaware that else where in the Solar System an identical relationship between a moon and a planet, has created a much more extreme tidal phenomena.
Gravity is a two way street.
Newton stated it in scientific terms, that every action there is an equal and opposite reaction.
So, not only does the moon exert a force on Earth,
the Earth exerts an equal and opposite force on the Moon.
Over hundreds of millions of years, this gravitational embrace between Earth and Moon,
has had a profound effect.
We only see one side of the moon facing Earth because the Moon is tidally locked.
Its rotation rate matches with its orbital period around the Earth.
This is not a coincidence, but a consequence of the gravitational interaction between Earth and Moon.
However on a daily basis, the impact of Earth’s gravity is minimal.
There is no liquid water on our Moon, and so there are no ocean tides.
The Earth’s gravity is too weak to have a significant effect on the Moon’s rocky constitution.
Half a billion kilometres away, we have discovered a different story in Jupiter.
The powerful gravitational bond that exists between one moon and its parent planet Jupiter,
has done something astonishing.
It has brought the moon to life, making it the most violent place in the Solar System.
400 years ago, Galileo was the first person to see Jupiter through a telescope.
Galileo observed three points of light around Jupiter.
He first described them as three little stars.
He quickly realised that they moved in relation to the planet,
disappearing from view and reappearing.
He correctly surmised that they must be objects orbiting Jupiter.
He catalogued the four largest moons of Jupiter.
In doing so he confirmed Copernicus’ revolutionary view of the Solar System.
No longer did our view of the Universe adhere to the Aristotlean view,
that all heavenly bodies orbit the Earth.
This unequivocally broke the divine symmetry of the Earth centred cosmos for good.
Jupiter’s four largest moons are named after the lovers of the Greek God Zeus.
Furthest out is Callisto, a ball of rock and ice, the size of Mercury,
and third largest moon in the Solar System.
Next is Ganymede, the largest moon in the Solar System.
It is the only moon to have its own internally generated magnetic field.
It may harbour a salt water ocean deep below its surface.
Next is icy Europa, the smoothest, most tantalising moon.
Evidence suggests that there is a vast ocean below its surface.
For many scientists, Europa is now the most likely candidate to harbour extraterrestrial life.
Finally, closest to Jupiter, is the small yellow tinged moon, Io.
Modern space probes have revealed that Io is an incredibly tormented world.
In 1979, the Voyager spacecraft became the first mission to study and photograph,
the moons of Jupiter close up, including the innermost Io.
Io is about the size of our Moon.
For 400 years we had assumed that it was a cold dead world.
A few weeks before Voyager arrived at Jupiter, 3 scientists made a prediction,
that appeared to be nothing more than fantasy.
Using the same physics that underpins our understanding of tides on Earth,
they predicted that Io should have an intense internal heat source,
because of its unique position in the Solar System.
Io orbits very close to massive Jupiter.
It is about the same distance from Earth to our Moon.
It is also surrounded by sister moons, Europa and Ganymede.
The configuration of moons and planets means Io,
is under the influence not just of the massive gravitational pull of Jupiter,
but also the additional pull of its neighbouring moons.
This gravitational tug of war has a miraculous effect on Io, transforming it from a dead world,
into one of the most dynamic geological bodies in the Solar System.
Io circles Jupiter every 1.77 days.
Crucially for every orbit of Io, Ganymede goes around about 4 times,
and Europa goes around just twice.
This beautiful symmetry is not a coincidence.
It is a consequence of the same complex gravitational dynamics,
that locked our Moon’s face forever towards Earth.
The technical term for this relationship is ‘orbital resonance’.
Periodically Io, Europa, and Ganymede line up together.
When they do Io gets a powerful gravitational kick on a regular basis.
This has the effect of forcing Io out of a nice circular orbit into an elliptical one.
Because Jupiter’s gravitational field is so great,
that it has the effect of continually stretching and squashing Io as it sails periodically closer to,
and farther from the planet.
This is exactly the same effect that creates the ocean tides on Earth.
In Io it is not water that is pulled and pushed, but the solid rock of the moon itself.
As Io is stretched and squashed repeatedly, it heats up by the friction,
transferring vast amounts of energy from its orbit to the rocky interior of the moon itself.
Over time, this vast energy transfer would cause Io’s orbit to become more circular.
But the elegant relationship between its orbit and its sister moons,
Europa and Ganymede ensures that it must continue its eccentric elliptical path around Jupiter.
This relentless gravitational tug of war keeps Io literally boiling hot,
moving rocks as if it were nothing more than water,
and transforming it into a world seething with heat, alive with volcanic activity.
The images sent back by Voyager confirmed what the scientists had predicted.
At the end of the last century, Galileo’s spacecraft took the best images we have of Io.
It helped to create a detailed picture of the geological life of the volcanic bubbling moon.
We now know that just one of the many lava lakes on Io,
releases more heat than all the Earth’s volcanoes put together.
The lava lakes on Io are vast.
The largest is 180 kilometres in diameter.
Io’s surface is covered by hundreds of volcanic centres.
It makes it the most volcanic place in the Solar System,
endlessly pumping out heat into the cold vacuum of space.
Io is a surprising and bizarre world.
Being so far from the Sun, its surface is about minus 155 degrees.
It is covered in frozen sulphur, giving it a rich yellow colour.
Yet amidst the frigid surface, Io is scarred by cauldrons of molten lava;
thousand of tons of flowing rock melted by energy,
extracted from Jupiter’s powerful gravitational field as it traces its eccentric orbital path.
Io’s unique gravitational connection to its parent planet,
provides a seemingly inexhaustible supply of heat.
As well as its huge lava lakes, the heat powers the largest volcanic eruptions in the Solar System.
Molten rock and gas blast out from the frigid surface.
The gas expands, shattering lava into giant fountains of fine particles.
With weak gravity and a sparse atmosphere, Io’s volcanic plumes tower over 300 kilometres.
This incredible phenomenon, volcanism comes from the simplest laws of physics.
The heat contained within the planet will eventually find a way to escape into space.
We have discovered that many moons in the Solar System are active, sometimes violent.
Io is fascinating.
It doesn’t derive its energy from a internal heat source, the same way as Earth does.
It extracts energy from its orbit around Jupiter.
We are living through the greatest age of discovery our civilisation has known.
We have voyaged to the farthest reaches of the Solar System.
We have photographed strange new worlds, stood in unfamiliar landscapes, and tasted alien air.
The one thing we have not found in these worlds, is the thing that makes our planet Earth unique: life.
Is Earth the only place in the Solar System that could support life, or are there other worlds that also, harbour the conditions to do so?
It is a great fundamental question for science.
It is also one of the great unanswered questions in human history.
The sea of Cortez, off the coast of Mexico is one of the most diverse ecosystems on the planet.
Thousands of sea creatures including blue whales can be found here.
The research vehicle Atlantis, is a regular visitor to this place.
On its board it has a legendary intrepid explorer of our deep oceans: Alvin.
Alvin is a 17 tonne, deep ocean submersible.
Built like a spacecraft, it is designed to take 3 humans on a 9 hour journey,
4600 metres below the ocean.
At these depths the pressure is 200 times the Earth’s atmospheric pressure.
Hidden 2000 metres below the surface, is one of the most bizarre environments on Earth.
Clustered around a hydrothermal vent - a volcanic opening in the Earth’s crust,
through which clouds of sulphurous chemicals pour into the ocean,
suspended in water heated to 300 degrees, is an underwater city.
It is created by energy released through the ever moving San Andreas fault.
Above the surface this fault is connected to destruction and death,
including the 1906 San Francisco earthquake, that devastated the city.
Below the fault does not take life, but creates it.
The vast majority of known life forms on Earth relies on energy from the Sun.
But deep down the ocean floor there is no sunlight to power them.
Some of the Sun’s energy does make it slowly down, in the form of decaying plant and animal debris,
from the higher levels of the ocean.
This biological material has captured the Sun’s energy via photosynthesis.
It delivers a slither of solar power to the ocean floor.
Yet it cannot meet the energy needs of the vast density of life,
we see living in the dark cold depths of the ocean.