Climate change
The changing climate of Venus
According toresearch,ourneighbour’senvironmenthaschangeddramatically
Gasandsteam
Impactsaddedadditional
materialtoVenus,includinga
significantamountofwater.
Coupledwiththeheatfrom
the magmaoceanandVenus’
proximitytotheSun,anearly
atmospherebegantoform
aroundtheplanet,largely
madeofcarbondioxideand
steam.Magmaocean
Just like the primitive Earth,
early Venus was still largely
molten as a result of the
high-energy impacts that
formed the planet in the
first place. This led to a
widespread ocean of magma
(molten rock) across the
planet, leading to very high
temperatures.Coolingand
condensing
Overtimethenumberof
impactsbegantodieaway;
theunbatteredplanetbegan
tocooldownanda solid
crustformedonthesurface.
Steamstartedtocondense
outoftheatmosphereand
fallasrain,creatingVenusian
lakes,riversandseas.Vociferousvolcanism
Deepinsidetheplanet,
underthecrust,themagma
oceanpersisted.Thisledto
wide-scalevolcanismacross
Venus.Todaywecanstillsee
thesevolcanoes,including
theplanet’stallest– Maat
Mons.Eruptionsaddedhuge
quantitiesofcarbondioxide
backintotheatmosphere.Globalwarming
Aswe’vediscoveredon
Earth,carbondioxideis
a powerfulgreenhouse
gas.Itletssolarenergyin,
butmakesithardforitto
escape.Overtimethishas
raisedthetemperatureon
Venus,farbeyondtheboiling
pointofwater.Nolakes,
riversorseasremain.STEP 1 STEP 2 STEP 4 STEP 5
© NASAdesigned to burrow into the Martian dirt. Among
its instruments is a thermometer – the Heat Flow
and Physical Properties Package, or HP3, perfect for
looking at Mars’ sub-surface heat.
Unfortunately the mission has been beset with
difficulties. On its first attempt the mole reached
a depth of just 35 centimetres (13.8 inches) before
getting stuck. Mission scientists are still trying to
puzzle out the problem and see if it can get as deep
as planned, but by their own admission it isn’t
looking promising. Detecting Attree’s predicted
excess now looks difficult. “We were only likely to
find it if the instrument was functioning perfectly,”
he says. All is not lost, however. There is another
way to keep track of Mars’ past climate cycles:
carbon dioxide. Today the gas that’s causing us so
many woes on Earth is the main constituent of
the Martian atmosphere. Yet the air is so thin that
the atmospheric pressure on Mars is just 0.6 per
cent of Earth’s. Carbon dioxide is also frozen intothe Martian ice caps. When changes to Mars’ orbit
and tilt increase the Sun’s intensity, the carbon
dioxide ice sublimates – turns straight from a solid
to gas – and carbon dioxide is added to the Martian
atmosphere. When things turn colder, the gas is
deposited back onto the ice caps. In the 1960s it
was predicted that the atmospheric pressure on
Mars cycles in this way, getting as low as four-times
less than today’s level and as high as double. Yet
evidence to back this up has remained elusive.
Then, in December 2019, a new study claimed to
have found it at long last.
It all hinges on the layers of carbon dioxide dry
ice and water ice on the planet’s south pole. A
kilometre (0.62 miles) deep, it contains as much
carbon dioxide as currently exists in the entire
atmosphere. Radar measurements from orbiting
satellites suggest the cap is formed of alternating
layers of dry and water ice. Dry ice trapped under
water ice shouldn’t be stable, yet it seems to persist.Left: Some
researchers
argue that
Ve nu s wou ld
have been a
potentially
habitable
planet long ago© NASASTEP 3