The exploration of our solar system is one of humanity’s greatest scientific achievements. The last fifty years in particular have seen huge steps forward in our understanding of the planets, the sun, and other objects in the solar system. Often referred to as the final frontier, many profound mysteries about our own solar system have yet to be answered.
In his book Exploring the Solar System, award-winning author Peter Bond takes a look at the latest information we have on the celestial bodies in our own backyard. Today he has agreed to talk with us about his work.
Science is often seen as a difficult subject to choose at school or college, and, as a result, students tend to avoid it. On the other hand, many young people are fascinated by space, and when I speak to school groups, they often show considerable knowledge of the stars and planets.
I wanted to write a book that would be accessible to students and general readers with a limited science background, one that would, hopefully, also enthuse and inspire them about the scientific discoveries that are being made about our solar system. Since we live on the only easily habitable planet in the solar system, it is also important to compare Earth with the other worlds that have been discovered, in order to make people aware of how unique and precious it is. Our role as caretakers of this beautiful blue planet cannot be overstated.
During presentations to groups of school students or non-scientists, I always try to give them an idea of sizes and distances. For example, when they see an image of Earth next to the Sun, they are amazed to discover that 1.3 million (1,300,000) Earths would fit inside the Sun. 1,300 Earths would fit inside Jupiter – indeed, Jupiter is so big that all of the other planets would fit inside it – yet it rotates faster than any other major planet, taking less than 10 hours to complete one rotation.
Similarly, I like to talk about what the other planets would be like to visit. On Venus, for example, the surface temperature is around 460 degrees Celsius (twice a domestic oven on maximum setting), air pressure is 90 times greater than on Earth (equivalent to what a deep sea diver would experience at a depth of 900 metres), the atmosphere is composed of carbon dioxide and sulphuric acid rain falls from the clouds. Hardly a good place to visit on holiday! No wonder most of the spacecraft to land on the planet ceased to operate after less than one hour.
At the other extreme, temperatures at Neptune and Pluto plunge to below minus 200 degrees Celsius. Fortunately, our Earth is a Goldilocks planet – not too hot or too cold, but just right!
When I was 10, my parents gave me a large, colourful book, entitled The Golden Book of Astronomy, as a birthday present. Its pages covered everything, from the stars, planets and galaxies to the apparent motion of the constellations across the sky. From then on, I was hooked. I read it over and over again, and even used it as the basis for a talk I gave to the other members of my class at school. I still have that wonderful book, even though most of its contents are now completely out-of-date.
There have been two golden ages of space exploration. The first of these was during the 1960s and 1970s, when humanity first set foot on the Moon and began to explore deep space. We are currently enjoying a second golden age, with spacecraft in orbit around Mercury, Venus, the Moon, Mars, Saturn and the asteroid Vesta. Meanwhile, the New Horizons spacecraft is en route to Pluto and the Kuiper Belt, and Rosetta is scheduled to rendezvous with, and land on, a comet, in 2014. Unfortunately, the global financial crisis is adversely affecting plans for future space exploration, with the likely prospect that the number and technological complexity of forthcoming missions will decline over the coming decade.
The landings of 12 Apollo astronauts on the Moon 1969-1972 must be the greatest technological and scientific feat of the space age. The treasure trove of rock samples and other data which they returned remains an invaluable source for modern researchers.
The American missions to Mars, especially the various roving vehicles, and the Soviet series of Venus landers which survived incredibly hostile conditions to send back data from the surface, were remarkable technological and scientific achievements. Particular mention should be made of the Mars Exploration Rovers, Spirit and Opportunity, which have rewritten the text books during their multi-year traverses over the varied Martian terrain. Hopefully, the nuclear-powered Curiosity rover, now on its way to Mars, will be just as successful.
I must mention two other missions which have achieved major breakthroughs. The NASA-ESA Cassini-Huygens mission to Saturn has a remarkable list of achievements, including the discovery of gaseous jets erupting from the moon Enceladus and the descent of Europe’s Huygens probe onto the hidden surface of Titan. The twin Voyager spacecraft, launched in 1977, unveiled the giant planets of the outer solar system, revealing planet-sized satellites, complex ring systems and turbulent atmospheres. Their feeble signals are still being received as they leave the Sun’s realm and venture into interstellar space.
The most fundamental question which may be answered in the not-too-distant future is one which has been asked since time immemorial: “Are we alone in the Universe?” The answer to this is most likely to come from analysis of rock samples drilled from deep beneath the Martian surface and then returned to Earth for analysis in terrestrial laboratories. More indirect evidence may come from the rapidly growing catalogue of planets in orbit around distant stars. Within a few years, ground-based instruments and space telescopes may combine to identify Earth-like worlds in the habitable zones around alien stars.
However, I have mixed feelings about the search for extraterrestrial intelligence. The first contact with an alien intelligence would be one of the most notable, and traumatic, events in human history. However, I have doubts about the ability of people and governments to be able to sensibly absorb and respond to this cultural and intellectual revolution.
All of the planets have their own unique characteristics, but funnily enough, I think I would have to say our Earth. It is the only place we know where life exists, and the only planet with surface oceans, and with a temperature which allows water to be present in the form of a gas, a liquid and a solid. There is so much to explore and study, from the glaciers and ice sheets, to hurricanes, ocean currents, deserts, mountain ranges, and slowly moving tectonic plates which result in earthquakes and volcanoes. We still don’t fully understand why ice ages occur, how the Sun influences our planet or the origin of life. By studying the other planets, we may find the answers to some of our questions about past, present and future conditions on Earth.
I must admit to being rather torn on this topic. I grew up regarding Pluto as the ninth major planet, the weird, tiny outpost of the solar system, and I was rather surprised when members of the International Astronomical Union decided to demote it to a dwarf planet. I can understand that Eris may be slightly larger than Pluto, and that even bigger objects may well be discovered in the future, but I am not convinced that this is a sufficient reason to list Pluto alongside Ceres, a much smaller asteroid. There is also controversy and dissension – with which I have some sympathy – over the way the IAU defines a planet / dwarf planet.
I’d like to mention three projects – all very different, but exciting and unusual in their own way.
The first of these was ESA’s Cluster mission to explore the Sun-Earth connection. Four identical spacecraft were built to fly in close formation around the Earth, passing in and out of the solar wind and the planet’s magnetic field. Unfortunately, after years of hard work and preparation, the quartet was destroyed when the Ariane 5 rocket exploded on its maiden flight.
Aware of the mission’s unique capability to provide 3-D mapping of near-Earth space, Agency officials and scientists supported a reflight, and Cluster rose like a phoenix from the ashes. As a member of the outreach team, I was able to follow Cluster’s progress from the depths of despair to the triumphal launches which took place in 2000. The satellites remain operational today.
Another ESA mission in which I was involved was Rosetta, the first attempt to send an orbiter and a lander to a comet. Once again, the development phase went – more or less – according to plan, and the spacecraft had already been shipped to the launch site when the launch was called off due to a major problem with the rocket. The prolonged postponement meant that the original comet could no longer be reached, and the Rosetta team was asked to identify a new target that the spacecraft could reach if launched within the next two-and-a-half years.
Once again, their efforts were rewarded, and Rosetta was duly sent on its way in March 2004. If all goes according to plan, it will rendezvous with comet Churyumov-Gerasimenko in 2014. It will then fly alongside the nucleus, monitoring the dramatic changes that take place as the icy object heads toward the inner solar system. Most exciting of all will be the first attempt to deliver a small lander onto the comet’s surface.
A very different project was the British Beagle-2 spacecraft, which piggybacked a ride on ESA’s Mars Express orbiter. Although the little lander was lost during the descent phase, it was a remarkable effort, led by Colin Pillinger and the Open University, and I was privileged to be part of the outreach team. I shall always remember the suspense and ultimate disappointment when the probe failed to call home.