(dreamy music)
Mars, our planetary neighbor.
It's very cold and dry
and its weak gravity only holds a thin atmosphere.
As probes started to visit the Red Planet,
we gained a more accurate view of the surface
and scientists began to wonder.
Mars had once been much warmer.
It had rivers, and in its early years,
might have sustained life.
(wind howling)
A succession of new techniques have been deployed,
trying to unlock the secrets of the Red Planet.
And while our knowledge of the Martian geology,
its atmosphere and its weather has grown immensely,
each new mission to Mars raises more questions
than it answers.
We still don't know if Mars has at some time
been a home to life.
(inspiring orchestra music)
In 1877, astronomer Giovanni Schiaparelli made
what he thought was the most accurate map of Mars yet drawn.
On it, he showed canals.
In the early 20th Century,
American astronomer Percival Lowell was convinced the canals
were signs of a civilization existing on the Red Planet.
So began the search for life on Mars.
In 1962, the Soviet Union sent the first probe, the Mars M1,
on a flyby mission.
It was an audacious project and it failed,
the first of many failures by both the
Soviet Union and the United States.
Cold War rivalry provided the motivation
for these early missions.
In 1971, NASA sent Mariner Nine to Mars.
It was the first probe to orbit another planet,
but scientists discovered that Mars was enveloped
in a planetary dust store.
On orbit photography revealed little more
than a red cloud.
Soon, Mariner Nine was joined by two Soviet orbiters,
both equipped with landers.
The Mars Two Lander crashed,
but the Mars Three lander made it to the surface intact.
It returned one garbled image and then stopped functioning.
Mars now had three orbiting spacecraft,
all looking at a dusty, featureless planet.
The two Soviet probes were identical,
but the American probe had one key design difference.
While the Soviet orbiters began photographing the planet
following predetermined schedules,
NASA were able to command Mariner Nine to wait
in hope that the dust would eventually settle.
It took months for the atmosphere to clear, but when it did,
Mariner Nine saw three craters protruding above the dust.
They were the tops of giant volcanoes
on what was called the Tharsis Plateau.
Soon, more complex geological features began to emerge.
In places, the surface was cratered,
suggesting the tectonic forces that constantly
renew the Earth's surface were absent on Mars.
Volcanic activity that built the solar system's largest
volcanoes had stopped billions of years ago.
This enabled NASA scientists to compile
an accurate global map of Mars
and to decide upon landing sites for the Viking probes
that followed in 1976.
Viking One and Two were identical orbiters,
with landers that both made successful landings
on the surface.
Both returned pictures of the Martian landscape.
The primary objective of the Viking program
was to find signatures of life,
but researchers now feel the three experiments tasked with
carrying out the analysis had limitations.
As researchers on Earth began looking
for traces of life in extreme environments,
they began to rethink where life on Mars might survive,
yet the consensus at the time was that Mars was sterile
and the idea of life on Mars died.
(mysterious music)
After a 20-year hiatus in Mars research,
Mars Global Surveyor went into orbit in 1996.
The pictures it relayed back were clearer than anything yet
seen from the Red Planet.
Although most Mars orbiters have been tasked with mapping
the planet's surface, this was different.
The high resolution images that the Mars Global Surveyor
sent back revealed rivers and even river deltas,
but the occasional impact crater suggested that nothing has
flowed in these systems for billions of years.
In July 1997, another probe arrived.
The Mars Pathfinder was one of a new breed of missions being
pushed by NASA's new administrator
under the guiding philosophy of faster, better, cheaper.
(wind howling)
The idea was to cut development times, cut budgets,
and although the risk of failure would rise,
the reduced price tag could mean more missions.
Pathfinder would land a small rover on the surface.
To do this, it used radically new airbag technology.
The technique drew more from automotive safety systems
than from previous space missions.
(engine roaring)
The landing site in Mars' Northern Hemisphere known
as Ares Vallis is one of the planet's rockiest areas,
yet it was thought to be a safe area to land.
The broad array of different rock types are believed to have
been deposited during an ancient flood.
The new landing technique worked perfectly and served as
a proof of concept that would be used on future missions.
(wind howling)
Pathfinder consisted of a base station equipped with three
solar panels that unfolded like petals.
There were sensors to measure atmospheric pressure,
air temperature, and wind speed,
as well as a transmitter to communicate with Earth.
In addition, Pathfinder acted as a base station
for the Sojourner Rover that explored the surrounding area.
Sojourner was fitted with cameras and an
alpha particle x-ray spectrometer.
It was the first mission to have its own website.
The rover returned thousands of images and important detail
about the atmosphere and geology and
its popularity guaranteed more Mars missions.
(engine roaring)
On the morning of April the 7th, 2001,
another Mars orbiter was launched.
Mars Odyssey was equipped with three primary instruments
and it had the ability to act as a relay satellite
between future surface missions to the Red Planet and Earth.
On its arrival at Mars,
it used a new technique to go into orbit.
After firing a relatively brief pulse of its engine,
Mars Odyssey went into a highly elliptical orbit,
that at its closest approach,
had it skimming the planet's thin upper atmosphere,
called aerobraking.
This technique allowed the craft to circularize its orbit
over a period of three months
and it saved around 200 kilograms of fuel.
The probe is still in operation today,
breaking all records as the longest serving Mars mission.
In December 2003, a new player arrived at Mars.
The European Space Agency, using a Russian launcher,
had sent Mars Express, its first planetary explorer.
It was equipped with a lander known as Beagle.
Though all contact was lost with the lander,
Mars Express continues to return valuable data.
The mission has been granted several extensions,
the latest till 2020.
Equipped with a high resolution stereo camera,
the probe returned unique 3D views of the planet's surface.
The orbiter determined that the polar ice caps
contain a blend of frozen CO2 and water ice.
In the atmosphere, Mars Express detected first methane
and then ammonia.
Both gasses deteriorate rapidly in sunlight,
so there must be sources on Mars continually producing them.
Methane and ammonia can rarely be made inorganically,
but they're generally associated with life.
One month after Mars Express went into orbit,
a NASA lander arrived at Mars,
followed three weeks later by a second identical craft.
(craft rumbling)
They were the Mars exploration rovers called
Spirit and Opportunity.
(wind howling)
Spirit, the first to land, was targeted at the Gusev crater.
Opportunity would land at the Meridiani Planum
on the opposite side of Mars.
(mysterious music) (wind howling)
Though they were much heavier than their
Pathfinder predecessor,
they used the same bounce landing technique.
Both landings were successful and on target.
After the craft had righted itself,
it detached from the lander and began autonomously unfolding
its solar panels and camera mass.
While this was happening,
the team back at the Jet Propulsion Laboratory waited.
Signals confirming the craft's safe arrival
took 15 minutes to travel back to Earth.
(crowd cheering)
Many of these people had invested years
of their lives in this project,
and the real mission had only just commenced.
(crowd cheering)
Both rovers were designed to operate for 90 Mars days.
A solar day on Mars is about 40 minutes longer
than an Earth day, and to avoid confusion,
the science team operating the rovers
refer to a Martian day as a sol.
Mission designers, knowing about the dust storms on Mars,
felt that the solar panels on the two rovers
would eventually be blocked with dirt and stop functioning,
but it became clear that the winds on Mars
were clearing the panels.
Soon, NASA announced that Opportunity had found evidence
confirming liquid water had once flowed on Mars.
There were pictures from the Meridiani Planum of stratified
patterns in the rocks, suggesting sedimentation.
The distribution of chlorine and bromine at the site were
clues to the area's past as the shore of a salty sea.
In April 2004, NASA announced it would extend the rovers'
missions from three to eight months.
It would be the first of many such mission extensions.
The rovers were equipped with an abrasion tool to grind away
a portion of a rock's surface for a more detailed,
uncontaminated analysis of geological samples.
This was first done by Spirit at a rock named
Adirondack at Gusev crater.
It was a first in planetary geology.
Researchers agonized before using the tool because of
the drain it makes on the rover's energy budget.
The rock was made of olivine, pyroxene, and magnetite,
making it very similar to volcanic basalt on Earth.
When Spirit's right front wheel stopped working,
engineers used a duplicate rover to devise
a reversing technique that enabled
the rover to drag its frozen wheel.
This left a furrow behind in the soil,
which presented a new area of research for the science team.
White or yellow deposits seen within the furrow were
various types salts that only form
in the presence of hot water.
On Earth, hot water provides an environment in which
microbes can thrive.
Spirit limped on for another three years before it
became stuck in loose sand.
Again, the engineers began working with a replica,
which they placed in an identical situation
When nothing was able to free the rover,
it was declared a stationary research platform.
Further attempts were made to position the rover
so its solar panels could operate more effectively,
but even this was not possible.
The last communication from Spirit was in March 2010.
Opportunity lasted until June 2018,
when dust clogged its solar panels.
In March 2006, NASA's Mars Reconnaissance Orbiter arrived at
Mars and began the now routine business of aerobraking.
Though this procedure took roughly six months,
the saving in fuel will see the craft functioning at Mars
into the 2030s.
One of the primary functions of the new orbiter
is as a communications relay station.
It's three meter antenna transmitting in the
ultra high frequency band enables very high data rates.
By November 2013,
it had tripled the amount of data sent to Earth by
all the other NASA missions combined.
Its high resolution camera began revealing
the surface of Mars in the finest detail.
These are active falling dunes in East Coprates Chasma.
The polar region, free of the seasonal dry ice,
again surrounded by dunes.
In the Southern Hemisphere,
pits in the residual cap of carbon dioxide.
(mysterious music) (wind howling)
The poles of Mars were now attracting keen interest.
Follow the water had become NASA's catchcry.
The Phoenix lander was targeted at the Northern polar region
to follow up on information from Mars Odyssey,
suggesting frozen water lay beneath
the surface near the poles.
Because imaging had revealed the region to be unvarying,
a rover was deemed unnecessary.
The lander had been designed to use a parachute decelerate
with rocket thrusters to deliver the craft to the surface
unlike NASA's previous three rovers, which had bounced.
This decision proved controversial as one strand of research
suggested the rocket fuel would contaminate
the very area that the lander was tasked with analyzing.
The craft waited 15 minutes to allow
any dust to settle before it deployed its solar panels.
Phoenix had landed during the early spring
in Mars' Northern Hemisphere,
so the solar panels would receive plenty of light
for the planned 90 day mission.
As well as its camera mass,
Phoenix was equipped with a meteorological station
that recorded the daily weather.
It featured a wind indicator and
pressure and temperature sensors.
In addition, a vertically pointed LIDAR
was able to observe cirrus clouds forming in the region
and snow falling in the polar atmosphere.
These phenomena had not been observed before.
The lander also had a robotic arm that could
dig half a meter into the soil
and deliver samples to the analyzer,
a combination of eight high temperature ovens
and a mass spectrometer.
In one excavation, the cameras recorded a white substance,
which gradually disappeared.
Given the temperatures and the time it lasted,
it could only have been water ice
that sublimated after it was exposed.
The soil was slightly alkaline and the presence of
perchlorate, which kills bacteria,
was not good news for those hoping for Martian life.
Phoenix operated for two months longer than planned
before the gathering winter completely
shaded its solar panel.
(upbeat music)
While the planet still had subterranean deposits of ice,
there was precious little left at the surface,
yet it was now understood that many of the Red Planet's
features had been carved by running water.
Samples analyzed from across the planet
affirmed that water and nothing else had made these changes
to the Martian landscape.
Mars had once been more like Earth,
yet it had lost its surface water
and most of its atmosphere,
and the question of life persisted.
Could it have emerged in a warmer, wetter past,
and could it still be present below the surface?
The next Mars mission would be NASA's most ambitious yet.
Known as Curiosity,
the car sized rover would be powered by a nuclear battery,
making it immune to the dust problems
experienced by Spirit and Opportunity.
Seven, six.
Curiosity was launched on an Atlas V
from Cape Canaveral in November 2011.
One.
Main engine, start.
Zero and lift off.
(engine rumbling)
In mid 2012,
it entered the Martian atmosphere heading for Gale crater.
The Jet Propulsion Laboratory monitored the entry closely,
but had no control over events.
In Mars' thin atmosphere,
the parachute could only slow the heavy craft
to around 320 kilometers per hour.
(engine rumbling)
Nearing the surface,
the rover descent stage dropped out of the aero shell
and rockets kicked in.
At this stage, radar was guiding the lander to the surface
and a small camera was recording images
of the terrain below the rover.
Next, Curiosity was lowered on a tether
beneath the descent stage.
This sky crane technique was used to
avoid too much swirling dust,
exposing the rover to unnecessary danger.
(engine rumbling)
(crowd cheering)
Everything had worked exactly as it was supposed to
and the American engineers were relieved.
The landing had been the most precise ever.
Before Curiosity could start work,
its computer went through a checklist to make certain that
all systems were operating correctly.
It was a day before the rover deployed its camera mass
and communications antennas.
It's thought that Gale crater is three and a half billion
years old and that its sediments have been
laid down first by water and then by wind.
NASA now has a sophisticated mobile science laboratory
on Mars connected to Earth by the most
advanced communications link,
courtesy of the Mars Reconnaissance Orbiter.
(satellite beeping)
The rover's primary objective is to discover if conditions
suitable for life ever existed or still exist on Mars.
It's also gathering detailed information about the current
conditions on the Red Planet,
particularly the radiation levels that will have an impact
on proposed manned missions.
Curiosity has analyzed the dust
from a number of holes it drilled,
revealing sulfur, nitrogen, hydrogen, oxygen, phosphorus,
and carbon, or elements essential to life.
In its six years on the surface of Mars,
Curiosity has traveled around 20 kilometers,
but the driving is taking its toll.
It routinely sends back a series of self-portraits,
mainly for diagnostic reasons.
Its wheels have taken severe damage,
which will undoubtedly lead to design changes
for future rovers.
Its computers are also giving problems,
but a new suite of missions is slated to arrive
at Mars in 2020 that will continue profiling the planet.
There is one aspect of the Martian environment
that has never been investigated,
but that's about to be addressed.
The Mars InSight probe has been targeted
at the flat Elysium Planitia, close to the equator,
to spend two years investigating the planet's interior.
It made a flawless landing in November 2018.
After unfurling its solar array,
it spent weeks selecting a suitable spot
to deploy a seismometer onto the surface
to monitor Mars quakes.
It's clear that Mars had a warm, wet past,
but it's cold and very dry now.
Learning about the planet's geological activity will help
us know why Mars has changed.
The InSight probe also hammered a thermal sensor into the
surface to gather data on heat flow from the planet's core.
By understanding processes within Mars,
we can learn how the geological histories of Mars and Earth
began to diverge.
(bright orchestra music)