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B
Series 10
All those craters
make the suface of
Mercury look a lot
like the Moon
efore travelling to a distant place we generally
do some research to find out what it has to
offer, how to get there and what equipment
we will need to take. This is precisely what
scientists have been doing for the past 50 years,
studying the planets in our solar system to discover
which ones are worth going to, whether it is possible
for humans to get there and what we might
expect to find if it is. We have dispatched
probes to pass by, orbit or land on
various bodies in the solar system,
compiling a sort of traveller’s guide
to our planetary neighbourhood.
Journey to
the planets
Mercury
Jupiter
Equatorial diameter: 4880km
Surface temperature: -180C to 425C
Average distance from the sun: 57.9 million km
Year: 87.9 Earth days
Travel time: Probe Mariner 10 took 147 days to reach
Equatorial diameter: 142,980 km
Surface temperature: -150C average
Average distance from the sun: 778.57 million km
Year: 4343 Earth days
Travel time: The New Horizons probe has taken the
Mercury from Earth
Earthly visitors: Visiting Mercury via space probes
has been difficult, because it is so close to the sun.
There have only been two journeys to Mercury: the first
being Mariner 10 in 1974 and the second MESSENGER
in 2008. However, further exploration is planned with
BepiColombo, a joint mission with the European Space
Agency and the Japanese Aerospace Exploration Agency,
planning to map the planet with two separate probes.
Things to see and do: Mercury’s surface has a
very thin atmosphere made up of particles whipped
up from its surface by solar winds but it is not enough
to stop meteors and asteroids hitting its surface. The
planet is pockmarked by craters, similar to our moon.
MESSENGER also revealed a lot of volcanic activity
on the planet. It has only about a third of the gravity
of Earth, so if a person could tolerate Mercury’s high
temperatures and lack of atmosphere they would be
able to jump three times as high there
as on Earth. The sun would look larger
to a person on Mercury, because the
planet is much closer to the sun than
Earth, but without much protection
from UV rays it wouldn’t be a
pleasant place to go sunbathing.
Pictur
e: NAS
A
fastest journey to Jupiter yet, making it in just 13 months
Earthly visitors: There have been fewer than 10 trips
by automated spacecraft to Jupiter, with only one probe
actually landing on the planet. A flight in 2011 is planned
with the objective to settle the debate on whether or not
Jupiter has a rocky core.
Mercury:
Under
meteor fire
BepiColombo:
Will arrive at
Mercury in
mid-2020
to birds than it does to humans. It is surrounded by layers
of gas and scientists are not yet sure whether there is
any solid ground to land on. If there is a surface, Jupiter
would not be a nice place for those who worry about their
weight, as people who weigh 100kg here on Earth would
weigh a whopping 250kg on Jupiter. The intense gravity
drags down comets, causing explosions on the planet
as large as Earth. Due to its intensely powerful winds,
Jupiter would be an excellent place to fly kites, provided
you avoided the frequent lightning and hurricane storms,
some of which are visible from Earth.
See the almost
Earth-size hole
made in Jupiter’s
atmosphere by a
comet in 2009
Equatorial diameter: 12,104km
Surface temperature:
-45C to 464C
Average distance from the
sun: 108.2 million km
Year: 224.7 Earth days
Travel time: 3.5 months
Earthly visitors: More than 50 attempts
have been made to send spacecraft to Venus,
the first in 1961. The next visit will be a part of the
BepiColombo mission, which will also visit Mercury.
Among the aims of this mission are to test Einstein’s
theory of general relativity and to search for asteroids.
Things to see and do: Venus is no place for
swimmers, because as the hottest planet in
the solar system its temperature is too hot
for water. However, Venus would be a great
place for partygoers because each day is
actually longer than each year. Venus takes
243 Earth days to turn fully on its axis but
takes 224.7 Earth days to orbit the sun. This
means it would be New Year’s day every
day, occasionally twice. Unfortunately,
even if we could survive the heat, Venus would
be a dangerous place to be as
90 per cent of its surface is volcanic.
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Pictur
e: Cou
r
tesy o
f ABC
Pluto
Equatorial diameter:
2324 km
Surface temperature:
-230C average
Average distance from
the Sun: 5900 million km
Year: 90,520 Earth days
Travel time: Although it is the planet furthest from
the sun, space scientists expect to reach Pluto in
less time than it took to reach the closer planets
Neptune and Uranus. They believe new technology
may allow us to reach Pluto in less than 10 years.
Earthly visitors: No spacecraft has ever reached
Pluto, although space probe New Horizons, launched
in 2006, is scheduled to land in 2015.
Things to see and do: Although formerly
recognised as a planet, Pluto has been downgraded
to a dwarf planet because it is is too small to be
distinguished from other similarly large objects
in the nearby Kuiper Belt. Many argue this is an
arbitrary definition that doesn’t really change
anything. If New Horizons can land in 2015, who
knows what it may find?
Cassini-Huygens
has a close
encounter with
Saturn’s rings
Saturn
Saturn: Made of gas and
Equatorial diameter: 116,340 km
surrounded by rings of debris
Surface temperature: -180C average
from asteroids and comets
Average distance from the sun: 1429.4 million km
Year: 10,759 Earth days
Travel time: Space probes that have travelled to Saturn have taken any time from three
to seven years
Earthly visitors: No spacecraft has been able to land on Saturn because of its gassy
nature, however the Cassini-Huygens spacecraft is presently in orbit. Saturn’s many
moons (46) mean future exploration is focused primarily on its satellites.
Things to see and do: It would be difficult to stand on Saturn, because it comprises
various gases and has no rocky surface. The planet is surrounded by thousands of tiny rings
grouped in seven different sections with each appearing as a single ring from Earth. These
rings are thought to consist of debris from asteroids, comets and meteors. If we could live
on Saturn, however, the planet itself could provide a source of energy, as it radiates
more energy than it receives from the sun, generated by its immensely hot core.
Venus: Far
too hot to
handle
Venus
Steve Squyre, principal investigator
NASA Mars Rovers program in Voyage
To The Planets, ABC1, May 13, 8.30pm
Things to see and do: Jupiter holds more of an appeal
Jupiter: Experiences
powerful winds and
frequent lightning
Picture: European
Space Agency
It’s the fact that it is so
much like Earth that makes
Mars such a special place.
Earth
Equatorial diameter: 12,756.3km
Surface temperature: -89C to 56.7C
Average distance from the sun: 149.6 million km
Year: 365 Earth days
Travel time: You’re already here
Extraterrestrial visitors: Number unknown
Things to see and do: Too numerous to mention
Valles Marineris:
The Grand
Canyon of Mars
Earth: Taken by
Japanese-built MTSAT-1R
geostationary satellite
Picture: NASA/
JPL/Arizona State
University
Mars
Equatorial
diameter:
6794 km
Surface temperature:
-140C to 20C
Voyager 2 is
13.8 billion km away
from Earth and still
sending back data
after 33 years
Mars: It has the
Average distance from
biggest canyon and
largest volcano in
the sun: 228 million km
the solar system
Year: 687 Earth days
Travel time: It took the Pathfinder probe seven
months to reach Mars but manned flights could take
as long as 18 months
Earthly visitors: Due to its proximity to Earth and similar
characteristics, Mars has been the object of many space
missions. Many were launched with the aim of
understanding if the planet
was habitable by human life.
The Viking missions in 1976 set out to
answer whether there is water and similar
important questions about the planet. The next
step would be a manned mission, but there has been no firm
commitment as yet.
Things to see and do: While a year on Mars is almost
double that of Earth, the days are approximately the same
length, with those on Mars being about 40 minutes longer.
This means if you were growing up on Mars you would be
about half the age you would be on Earth, without having to
miss out on any of your day or night time. If you are one for
the outdoors, you could also go sightseeing on Mars, which
has the biggest canyon in the solar system and the largest
volcano. Compared with the other planets Mars seems
relatively safe as its volcanos are apparently inactive.
Uranus: Seasons last
20 years instead
of three months
as on Earth
Neptune
Equatorial diameter: 49,532km
Surface temperature: -220C average
Average distance from the sun:
4504.3 million km
Year: 60,148 Earth days
Travel time: Voyager 2 to Neptune
in 12 years
Earthly visitors: There has been no landing
on Neptune. Voyager 2 has reached the planet
and is currently within Neptune’s orbit.
Things to see and do: Although Neptune
looks pretty from afar, it may not be so appealing
up close. Its beautiful shade of blue is actually
produced by methane gas in the atmosphere,
meaning Neptune could be a particularly smelly
place to visit. A sight to see is Neptune’s famous
“scooter”, a constant cloud that moves around the
planet about every 16 hours along with the solar
system’s most intense storms, with winds blowing
three times stronger than the most powerful
hurricane on Earth.
Picture: NASA
Uranus
Sources and further study
n Voyage To The Planets, Thursdays 8.30pm,
Equatorial diameter: 51,118km
Surface temperature: -214C average
Average distance from the sun: 2870 million km
Year: 30,660 Earth days
Travel time: Voyager 2 took nearly nine years to simply fly past the planet
Earthly visitors: No spacecraft has landed on or orbited Uranus, although
Voyager 2 did a fly-past in 1989.
Things to see and do: If you like winter months, Uranus could be the holiday
planet for you. Because the planet spins on its side, each season lasts approximately 20
years. It is also the coldest planet in the solar system, radiating minuscule amounts
of heat in comparison to other planets. You can actually see
Uranus with the naked eye, despite it being
so far away.
ABC1, May 13 to June 17
n Australian Backyard Astronomy, by Dr Ragbir
Bhathal and Jenny Bhathal (National Library
of Australia)
n The Universal Book Of Astronomy, by
David Darling (Wiley)
n The 8 Planets nineplanets.org
n NASA Worldbook www.nasa.gov/worldbook
n Encyclopaedia Britannica
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