ONE STRANGE ROCK
6 THINGS THAT MAKE LIFE ON EARTH POSSIBLE
Earth is well equipped as a planet and ideally placed in our solar system and galaxy to support life as we know it. The product of some 4.6 billion years of cosmic construction, our planet is flush with life thanks to a fortuitous set of conditions.
BY MANUEL CANALES, MATTHEW W. CHWASTYK, AND EVE CONANT
MANUEL CANALES, MATTHEW W. CHWASTYK, Soren walljasper, ryan t. williams, ngm staff; SEAN MCNAUGHTON
art: ANTOINE COLLIGNON, tomÁŠ müller
Sources: PETER D. WARD, University of Washington; Kate Maher, Stanford University; Karina A. YAGER, NASA Goddard Space FLight Center; jason Barnes, University of IdahO, GUILLERMO GONZALEZ, BALL STATE UNIVERSITY; MICHAEL GOWANLOCK, NORTHERN ARIZONA UNIVERSITY; ICARUS; ASTROBIOLOGY; NASA/JPL; INTERNATIONAL JOURNAL OF ASTROBIOLOGY
20,000
light-years
10,000
light-years
Core
YOU ARE HERE
SOLAR SYSTEM
Proxima Centauri
AD Leonis
Eta Cassiopeiae A, B
Altair
Eta Cassiopeiae A, B
Altair
SUN
Procyon A, B
Alpha Centauri A, B
Sirius A, B
Delta Pavonis
SUN
Relative size
of the Earth
Solar flare
neptune
Uranus
sun
earth
Mercury
About 93 million miles
from Earth to Sun
venus
WE HAVE A BIG MOON TO
STABILISE OUR AXAIL WOBBLE
moon
earth
The moon is a
relatively large
2% of the Earth’s
volume.
1
Our location is far from
MANY HAZARDS
The solar system is comfortably nestled in a safe harbour
between major spiral arms, and its nearly circular orbit helps
it avoid the galaxy’s perilous inner regions. There are
relatively few stars near the sun, reducing risks to Earth
from gravitational tugs, gamma-ray bursts, or collapsing
stars called supernovae.
10,000
light-years
20,000
light-years
Core
YOU ARE HERE
SOLAR SYSTEM
Proxima Centauri
AD Leonis
Eta Cassiopeiae A, B
Altair
SUN
Procyon A, B
Alpha Centauri A, B
Sirius A, B
Delta Pavonis
2
Our SUN IS A STABLE AND LONG-
LASTING STAR
Stars more massive than the sun burn hotter and usually
don’t live long enough for planets to develop life. Less
massive, younger stars are often unstable and are prone to
blasting their planets with bursts of radiation.
SUN
Relative size
of the Earth
Solar flare
3
we’re at just the right
distance from the sun
Earth orbits in the so-called Goldilocks zone, where the planet
receives enough energy to allow water to exist as a liquid
on its surface. Too far, and the vital compound stays locked
up as ice. Too close, and the water would rapidly
evapourate into the atmosphere.
neptune
Uranus
sun
earth
SATURN
Mercury
About 93 million miles
from Earth to Sun
venus
4
we have the right stuff to
host a dynamic core
The interstellar cloud of gas and dust that gave rise to
Earth contained enough radioactive elements to power a
churning core for billions of years. This creates a magnetic
field that protects the planet from
dangers like solar flares.
Currents in Earth’s molten
outer core generate our
magnetic field.
earth
5
we have A BIG MOON TO
STABILISE OUR AXAIL WOBBLE
Earth is tilted with respect to the sun, and teeters as it spins.
This tiny wobble can shift the climate from hot to icy every
41,000 years—and might vary more without the
moon's stablilising pull.
moon
earth
The moon is a
relatively large
2% of the Earth’s
volume.
1
Our location is far from
MANY HAZARDS
The solar system is comfortably nestled in a safe harbour
between major spiral arms, and its nearly circular orbit helps
it avoid the galaxy’s perilous inner regions. There are
relatively few stars near the sun, reducing risks to Earth
from gravitational tugs, gamma-ray bursts, or collapsing
stars called supernovae.
20,000
light-years
10,000
light-years
Core
YOU ARE HERE
SOLAR SYSTEM
Proxima Centauri
AD Leonis
Eta Cassiopeiae A, B
Altair
SUN
Procyon A, B
Alpha Centauri A, B
Sirius A, B
Delta Pavonis
2
Our SUN IS A STABLE AND LONG-
LASTING STAR
Stars more massive than the sun burn hotter and usually
don’t live long enough for planets to develop life. Less
massive, younger stars are often unstable and are prone to
blasting their planets with bursts of radiation.
SUN
Relative size
of the Earth
Solar flare
3
we’re at just the right
distance from the sun
Earth orbits in the so-called Goldilocks zone, where the planet
receives enough energy to allow water to exist as a liquid
on its surface. Too far, and the vital compound stays locked
up as ice. Too close, and the water would rapidly
evapourate into the atmosphere
neptune
Uranus
sun
earth
Mercury
SATURN
About 93 million miles
from Earth to Sun
venus
4
we have the right stuff to
host a dynamic core
The interstellar cloud of gas and dust that gave rise to
Earth contained enough radioactive elements to power a
churning core for billions of years. This creates a magnetic
field that protects the planet from
dangers like solar flares.
Currents in Earth’s molten
outer core generate our
magnetic field.
earth
5
we have A BIG MOON TO
STABILISE OUR AXAIL WOBBLE
Earth is tilted with respect to the sun, and teeters as it spins.
This tiny wobble can shift the climate from hot to icy every
41,000 years—and might vary more without the
moon's stablilising pull.
moon
earth
The moon is a
relatively large
2% of the Earth’s
volume.
6
we have an ozone layer to block
harmful rays
Ancient plantlike organisms in the oceans added oxygen to the
atmosphere and created a high-altitude layer of ozone that
shielded early land species from lethal radiation.