Universe is around 15 billion years, then the Earth was probably formed 4.1 billion
years ago from the same matter as that found on other planets (Dalrymple 2001).
The continued exploration of our planet can provide us with an opportunity to
better understand the extraterrestrial bodies in the rest of our universe.
Recently, more information on the composition of our galaxy has come from
spacecraft sent into space to collect data and make in situ measurements of meteorites and comets. For example, the Comet Wild 2 images and dust samples collected from the NASA Stardust and Deep Impact missions gave us some information
on the nature of the solid material in comets (From Internet: news.com.au). The
presence of minerals called fosterite (Mg 2 SiO 4 ) and enstatite (MgSiO 3 ) along with
other phases have been detected in meteorites (Brownlee 2008), and these minerals
are similar to the mineral composition found in our own Earth’s mantle.
Our nearest neighbor, planet Mars with its lower density, is also one of the
smallest planets in our solar system. It has been explored by robots carrying out
geological and biological experiments. So far, little has been achieved to determine the existence of water (H 2 O) such as we know it on Earth. Mars’ atmosphere
has a low density and it is very cold (-93 °C to 13 °C), so it is unlikely that water
could exist in its liquid form.
In 2004, based on satellite observations on Mars, scientists detected the existence of an ice cap located on the South Pole of this planet using a spectrometer
capable of detecting images in the range of infrared sensors. This ice cap is not
made of water, but is formed of frozen CO 2 (Pappalardo et al. 1998). If liquid
water (H 2 O) could have been present on Mars in the past, this might suggest the
existence of life on the planet. However, the thin CO 2 -rich atmosphere does not
prevent incoming UV (ultra violet) radiation from the Sun, which is fatal for living
organisms.
On the other hand, on Europa, which is a moon circling around Jupiter, we have
observed a liquid ocean covering its surface. Is this ocean similar to that of our
Earth? The Galileo space probe permitted us to observe patchy structures on the
surface of Europa that were interpreted by scientists as representing floating icebergs (Pappalardo et al. 1998).
It was in 2004 that the Cassini-Huygen spacecraft entered Saturn’s orbit.
Landing on Titan, one of the largest moons of Saturn, scientists interpreted evidence of frozen methane as being flat and rounded slabs (Pappalardo et al. 1998).
NASA scientists have announced that they were able to photograph features
resembling lakes of liquid hydrocarbons more than 200 km long and 70 km wide.
The Solid Earth’s Interior
Probably the Earth’s interior today does not reflect the composition and the
structure that it must have had at the beginning. During the creation of the solar
system, crystalline solids condensed from the solar nebula. These solids were
swept up by gravitational attraction after which intense heating and melting took
26
2 Our Haven, Planet Earth
years ago from the same matter as that found on other planets (Dalrymple 2001).
The continued exploration of our planet can provide us with an opportunity to
better understand the extraterrestrial bodies in the rest of our universe.
Recently, more information on the composition of our galaxy has come from
spacecraft sent into space to collect data and make in situ measurements of meteorites and comets. For example, the Comet Wild 2 images and dust samples collected from the NASA Stardust and Deep Impact missions gave us some information
on the nature of the solid material in comets (From Internet: news.com.au). The
presence of minerals called fosterite (Mg 2 SiO 4 ) and enstatite (MgSiO 3 ) along with
other phases have been detected in meteorites (Brownlee 2008), and these minerals
are similar to the mineral composition found in our own Earth’s mantle.
Our nearest neighbor, planet Mars with its lower density, is also one of the
smallest planets in our solar system. It has been explored by robots carrying out
geological and biological experiments. So far, little has been achieved to determine the existence of water (H 2 O) such as we know it on Earth. Mars’ atmosphere
has a low density and it is very cold (-93 °C to 13 °C), so it is unlikely that water
could exist in its liquid form.
In 2004, based on satellite observations on Mars, scientists detected the existence of an ice cap located on the South Pole of this planet using a spectrometer
capable of detecting images in the range of infrared sensors. This ice cap is not
made of water, but is formed of frozen CO 2 (Pappalardo et al. 1998). If liquid
water (H 2 O) could have been present on Mars in the past, this might suggest the
existence of life on the planet. However, the thin CO 2 -rich atmosphere does not
prevent incoming UV (ultra violet) radiation from the Sun, which is fatal for living
organisms.
On the other hand, on Europa, which is a moon circling around Jupiter, we have
observed a liquid ocean covering its surface. Is this ocean similar to that of our
Earth? The Galileo space probe permitted us to observe patchy structures on the
surface of Europa that were interpreted by scientists as representing floating icebergs (Pappalardo et al. 1998).
It was in 2004 that the Cassini-Huygen spacecraft entered Saturn’s orbit.
Landing on Titan, one of the largest moons of Saturn, scientists interpreted evidence of frozen methane as being flat and rounded slabs (Pappalardo et al. 1998).
NASA scientists have announced that they were able to photograph features
resembling lakes of liquid hydrocarbons more than 200 km long and 70 km wide.
The Solid Earth’s Interior
Probably the Earth’s interior today does not reflect the composition and the
structure that it must have had at the beginning. During the creation of the solar
system, crystalline solids condensed from the solar nebula. These solids were
swept up by gravitational attraction after which intense heating and melting took
26
2 Our Haven, Planet Earth