Another Atlas exclusive essay written by the indefatigable historian Fjordman. This the third and final part of his history of geology and planetary
science. Part one can be read here and part two here.
A History of Geology and Planetary Science
Fjordman
Auroras in the
Northern Hemisphere are called
northern lights; in the Southern Hemisphere southern
lights. They appear as arcs, clouds and streaks
which move across the night sky. The most common colors are green and red,
although other colors may occur, too. Auroras have been observed on some
other planets such Jupiter and Saturn as well, caused by their strong magnetic
fields. They become more spectacular the closer you get
to the Arctic or Antarctic regions, which is one of the reasons why their nature
was finally worked out in Scandinavia.
The Swedish
astronomers Anders Celsius and Olof Hiorter (1696-1750) in 1741
studied the aurora borealis and noticed that it
disturbed magnetic compass needles, although they could not fully explain why. While in Paris,
Celsius had become acquainted with
the French naturalist Pierre-Louis de Maupertuis (1698-1759) who supported
Isaac Newton’s theory that the shape of the Earth swelled near the equator and
slightly flattened near the poles.
To settle the matter, in 1736 the French
Geodesic Mission sent one expedition to Scandinavian Lapland under Celsius and
Maupertuis and another to Ecuador close to the Equator. Their measurements
proved that Newton’s theory was correct. Maupertuis is also remembered for
advocating the physical principle of least action and for his work on heredity
before the nineteenth century theories of evolution by the naturalist
Jean-Baptiste Lamarck in France and those of Charles Darwin and Alfred Russel
Wallace in Britain.
At Göttingen in Germany, the
physicist Wilhelm Weber (1804-1891) cooperated closely with
the brilliant mathematician Carl Friedrich Gauss. The
German naturalist and explorer Alexander von Humboldt
in 1805 reported that magnetic intensity varied across the Earth’s surface and
encouraged the establishment of an international network of magnetic
observatories. By the 1830s Gauss and his younger collaborator Weber took over from Humboldt as leaders in geomagnetism. Accurate measurements
were emphasized by both of them as they realized that these were crucial for
developing and verifying physical laws.
During the Enlightenment it
had been established that air can be electrically charged. In 1752
the Danish-Norwegian professor and bishop Erik Pontoppidan (1698-1764) suggested that the aurora borealis is an
electrical phenomenon. The Scottish physicist Balfour
Stewart (1828-1887), who studied
terrestrial magnetism, in the 1880s proposed the existence of electrical
currents in a high, conductive layer in the atmosphere to explain geomagnetic
variations.
At this time the physical chemist Svante Arrhenius
(1859-1927) from Sweden was developing his theory of ionic bonds, formed by the
attraction between two ions with opposite charges. One example of this would be
common table salt (NaCl). In the early 1800s the great English naturalist
Michael Faraday had suggested that charged particles which he termed “ions” were
formed by the process of electrolysis, but Arrhenius’ work led him to believe that
electrolytes contain ions even when they are not exposed to
electricity.
Ions are atoms that have acquired positive or negative net electric charge
due to losing or gaining one or more electrons.
The ionosphere is a layer of ionized air in
the upper atmosphere, extending from about 80 km, where radiation from the Sun
and to a lesser extent cosmic rays break apart molecules and atoms of air,
leaving ions and free-floating electrons.
In 1902 the
Italian physicist and radio
pioneer Guglielmo Marconi successfully sent radio waves across the Atlantic Ocean.
The English physicist Oliver Heaviside
(1850-1925) and the American electrical
engineer Arthur E. Kennelly (1861-1939)
in 1902 independently predicted the existence of a conducting reflective
layer that was bouncing radio waves back to the ground over vast distances in
spite of the Earth’s curvature. The gifted English physicist Edward Appleton (1892-1965), who had studied
under J. J. Thomson and Ernest Rutherford, in 1924 through a series of
experiments proved the existence of the layer in the upper atmosphere now called
the ionosphere. The ionosphere’s existence was fully
established about 1930 by Appleton and Douglas R. Hartree (1897-1958) in
Britain. Further studies of this layer were carried out by the English
geophysicist Sydney Chapman (1888-1970).
The Norwegian physicist Kristian Birkeland
(1867-1917) grew
up in Kristiania (Oslo) and at the turn of the
twentieth century undertook expeditions to near-Arctic regions to study
aurora currents. He hypothesized that
they were caused by the interaction of energetic particles from outside of the
atmosphere with atoms of the upper atmosphere. He managed to experimentally
reproduce the Solar System in miniature in his laboratory. He placed a
magnetized sphere, a “terrella” representing the Earth, inside
a vacuum chamber, aimed a beam of electrons towards it and could see that they
were steered by the magnetic field to the vicinity of its magnetic poles.
Birkeland’s ideas were nevertheless rejected by most scientists at the time and
were only verified by satellites generations later. Even a brilliant man such as
Lord Kelvin in 1892 erroneously
stated that no matter passes between the Sun and the Earth.
In a drive to
finance his often expensive research, Birkeland teamed up with the Norwegian
industrialist Samuel Eyde (1866-1940) and invented the first industrial scale
method to extract nitrogen-based fertilizers from the air. However, by the 1920s
their method was no longer able to compete with the Haber-Bosch process.
The German Jewish scholar >Fritz Haber<(1868-1934)
invented a
process, further developed by Carl Bosch (1874-1940), for mass production of
nitrates, which in turn permits the mass production of fertilizers and
explosives. Incidentally, Haber was also one of the
developers of chemical warfare during World War I.
One large piece of the puzzle was the discovery of
zones of highly energetic charged
particles trapped in the Earth’s magnetic field. After the
Soviet Union in 1957 launched the world’s first
artificial satellite into orbit, the Sputnik 1, the United States launched its
own Explorer 1 in 1958 whose Geiger counter detected a powerful radiation belt
surrounding the Earth. This was the first major scientific discovery of the
Space Age. The Van Allen radiation belts, named after the American space
scientist James Van Allen (1914-2006), consist of two distinct parts, one inner and one outer belt,
formed by somewhat different physical processes.
In 1959 the astrophysicist
Thomas Gold (1920-2004) proposed the name “magnetosphere” to the
highly magnetized region of space where a planet’s
magnetic field dominates the plasma of the solar wind. The magnetosphere has
a teardrop shape because it is compressed on the Sun side while its tail is pushed away from the Sun, similar to comet tails. Studies of comet tails by the German astronomer Ludwig Biermann (1907-1986) and others led to successful
predictions of the solar wind and of the hydrogen halos around
comets.
Hans Christian Ørsted in Denmark in 1820 found a connection
between electrical and magnetic phenomena and opened up the study of
electromagnetism. The French mathematical physicist and
astronomer François Arago described the generation of magnetism by rotation in
the 1820s, and his observations were expanded by Michael Faraday. As we have
seen, the existence of a liquid outer core separated
from a solid inner core inside the Earth was discovered in 1936 by the
seismologist Inge Lehmann from Denmark. The German-born physicist Walter
M. Elsasser (1904-1991) in 1946
published his theory that the Earth’s electromagnetic field is generated by an
internal dynamo in the rotating, liquid outer core.
According to our best estimates, the planet Jupiter consists of almost 90% hydrogen
and 10% helium by numbers of atoms, or 75/25% by mass, with additional traces of
methane, water, ammonia and other chemical substances. This is believed to be
close to the composition of the primordial solar nebula which existed 4.6
billion years ago. Saturn has a similar composition. The
intense radiation surrounding Jupiter would be fatal to humans; its
magnetosphere is immense and in volume even bigger than the Sun itself, making
it arguably the largest structure in our Solar System. It is believed that
Jupiter’s magnetic field is generated by an internal
dynamo caused by the circulation of metallic hydrogen in that planet’s outer
core.
The English geophysicists Sydney
Chapman and Vincent Ferraro (1907-1974) in 1930 proposed that the Sun emits huge
clouds of plasma, containing equal numbers of positive ions and electrons. It
has since then been established that the Sun emits plasma at great speed at all
times, not merely during magnetic storms as Chapman and Ferraro had assumed.
This is the solar wind, whose existence was predicted in 1958 by the
astrophysicist Eugene Parker (born 1927) at the
University of Chicago in the USA against strong opposition. He developed his
models when observations of comet tails still provided most of the available
data. Parker’s work has greatly increased our understanding of the magnetic
fields of the Earth and the Sun.
The American astronomer Fred
Whipple (1906-2004) in 1950 proposed the
“dirty snowball” model for comet nuclei, where comets have icy cores inside thin
insulating layers of dirt. Whipple believed that jets of material ejected as a
result of solar heating were the cause of minor orbital changes of comets. This
model is still held to be correct. The nucleus contains
a mixture of dust and water ice with elements of frozen carbon dioxide, methane
and ammonia.
Comets are frozen remains of
the nebula that formed our Solar System. As they approach the Sun, heat vaporizes some of
the frozen materials so that the comet’s nucleus spews gas and dust particles
into space. Around the nucleus, which is normally a few kilometers in diameter,
comets develop a cloud of diffuse material called a coma. Comet tails are pushed away
by solar radiation and the solar wind and consequently always point away from
the Sun. Some scientists believe that comets originally brought to the young
Earth some of the water and carbon-based molecules that make up living things,
although whether substantial amounts of water were
brought from comets to our oceans has been disputed based on chemical
analysis.
Large sunspots may under certain conditions
be seen by the unaided eye, but the modern study of them began around 1610 with
the introduction of the telescope. Sunspots are strongly magnetic and appear
darker because they are slightly cooler than the regions that surround them.
Based on daily observation records between 1826 and
1843, the German amateur astronomer
Heinrich Schwabe (1789-1875), a pharmacist living in the town of Dessau, in 1843 announced that sunspots vary in number in
a cycle of roughly ten to eleven years. He was
originally looking for a yet-unknown planet moving inside the orbit of Mercury.
His article caught the eye of
Alexander von Humboldt, who in 1851 published Schwabe’s table updated to 1850.
After that many scientists became interested in the 11-year sunspot
cycle. It has later been established that periods with many sunspots
correspond to high solar activity.
The Swiss astronomer Rudolf Wolf (1816-1893) had studied at the
universities of Zürich, Vienna and Berlin, where the German astronomer Johann
Franz Encke was one of his teachers. Wolf became director of the Bern
Observatory in Switzerland in 1847 and in 1848 devised the “Zürich sunspot
number” to gauge the number of sunspots.
A gentleman of independent means, the
English amateur astronomer Richard Carrington
(1826-1875), devoted himself to the study of sunspots.
Carrington
found by observing their motions that the Sun rotates faster at the equator
than near the poles. Another early pioneer in the study of sunspot cycles was the German
astronomer Gustav Spörer (1822-1895).
The Anglo-Irish geophysicist Edward
Sabine (1788-1883) in 1852 found an
association between the sunspot cycle and the occurrence of large magnetic
storms. On September 1, 1859, Richard Carrington in England through his
telescope, which projected an 11-inch-wide image of the Sun on a screen,
observed what we now know was a huge solar flare, a magnetic explosion on the
Sun. Only 17 hours later this event triggered a large magnetic storm on the
Earth. Just before dawn the next day, auroras occurred even in Cuba and Hawaii.
Spark discharges shocked telegraph operators in several regions and set
telegraph paper on fire.
Unusual solar activity can cause geomagnetic
storms (disturbances in the Earth’s magnetosphere) and interrupt electromagnetic
communications, for instance by affecting the ionosphere. A powerful solar flare
of the strength observed by Carrington could potentially cause quite serious
damage today due to our much more extensive reliance on electromagnetic
equipment and communications in the twenty-first century as compared to the
mid-nineteenth.
Early estimates of stellar surface temperatures made using
Newton’s law of cooling gave far too high temperatures. More accurate values
were obtained by using the radiation laws of the Slovenian physicist Joseph
Stefan in 1879 and the German physicist Wilhelm Wien in 1896. Stefan calculated
the temperature of the Sun’s surface to about 5400 °C, which was the most
sensible value by date. Stefan’s Law or the Stefan-Boltzmann Law, named after Stefan
and his Austrian student Ludwig Boltzmann, suggests that the amount of radiation
given off by a body is proportional to the fourth power of its temperature as
measured in Kelvin units.
The part of the
Sun that we
normally see has a temperature of more than 5500 degrees C, almost 5800 K.
Temperatures in the core, where nuclear fusion occurs, reach over 15 million K.
The lowest layer of the atmosphere is called the photosphere. The next zone is
the chromospheres, where the temperature rises to 20,000 K. The corona, the
Sun’s outer atmosphere, is remarkably hot. In the part nearest the surface the
temperature is 1 million to 6 million K, but it can reach tens of millions of
degrees when a flare occurs. Sunspots are cooler regions where magnetic energy
builds up and is often released in
solar flares and discharges of charged particles known as coronal mass
ejections. These events can trigger space storms that affect the Earth. The flow
of coronal gas into space is known as the solar wind. The corona is visible
during total solar eclipses as a large halo of white, glowing gas, but the
relative rarity of such eclipses present logistical difficulties for detailed
observations.
The technical problems associated with
producing an artificial eclipse to study the Sun were solved by the French
solar physicist Bernard Lyot
(1897-1952), an expert in optics who had studied engineering in Paris in addition to mathematics, physics and
chemistry. As an astronomer, Lyot found that the lunar surface behaves like
volcanic dust and that Mars has sandstorms. In 1930 he invented an
instrument known as the coronagraph, a telescope equipped with an
occulting disk sized in such a way as to block out the solar disk, which is more
difficult than it sounds. By 1931 he was
obtaining photographs of the corona. He found new spectral lines in the corona
and made the first motion pictures of solar prominences.
In the 1930s, Lyot boldly inferred a coronal temperature of around 600,000 K. This
claim was met with skepticism at the time. Acceptance of these very high
temperatures came through the spectroscopic work of the German astrophysicist
Walter Grotrian (1890-1954) and the Swedish astrophysicist Bengt Edlén
(1906-1993) soon after, but an explanation for how the Sun’s upper atmosphere
could be so much hotter than its surface took a long time to work
out.
The Swedish physicist Hannes Alfvén (1908-1995) was one of the
founders of plasma
physics and
magnetohydrodynamics, the study of plasmas in magnetic fields. Alfvén was born in Norrköping, Sweden. Both his parents were practicing physicians. He
studied at Uppsala University and became a research physicist and professor in
Stockholm. He made many discoveries in solar and space plasma physics and his
work on cosmic rays led him to propose in 1937 the existence of a galactic
magnetic field. The one discovery for which he is best known is the
magnetohydrodynamic wave commonly called the Alfvén wave, whose existence for
decades was difficult to prove. Finally in 2009, pictures taken by a team using the
Swedish Solar Telescope in Spain’s Canary Islands revealed that “corkscrew”
waves - Alfvén waves – were pushing heat from the Sun’s surface to its outer
atmosphere, the corona.
The amount of energy the Sun puts out varies
over an 11-year cycle which also governs the appearance
of sunspots. While that cycle changes the total amount of solar energy reaching
the Earth only by a tiny fraction, perhaps 0.1 percent, this small variation
appears to be sufficient to affect our weather patterns; by how much remains a
field of active research. We know that a period with very few sunspots called
the Maunder Minimum, named after the English astronomer
Edward Maunder (1851-1928),
began around 1650, at the same time as a period of unusually cold weather called
the Little Ice Age. Was this merely a coincidence?
Henrik Svensmark (born 1958) from
the Center for Sun-Climate Research at the Danish National Space Center in
Copenhagen, Denmark, has proposed that solar activity and cosmic rays are
instrumental in determining the warming of the Earth. He builds on the work of
space physicist Eigil Fiin-Christensen who with Knud Lassen Fiin in 1991 looked
at solar activity over the last century and found a remarkable correlation to
temperatures on our own planet.
Cosmic rays are energetic particles, most of them protons,
originating from outer space. Galactic cosmic rays are subatomic
particles - protons along with some heavy nuclei - accelerated to velocities
approaching the speed of light by distant supernova explosions. In addition to
being modulated by the Earth’s magnetic field these have to enter into the
heliosphere, the protective bubble stretching far beyond the orbit of Pluto
where the solar wind, the plasma of electrons and atomic nuclei constantly
ejected from the Sun, dominates interstellar space. When solar activity is
strong, the solar wind allows fewer external cosmic rays to reach our Solar
System and our planet.
Henrik Svensmark and his colleagues
carried out a landmark study of cosmic rays and clouds. They demonstrated
that such rays could produce small aerosols, the basic building blocks
for cloud condensation nuclei. The condensation of clouds affects the energy
balance and by extension the temperature on Earth. They received support for
these studies from the Danish Carlsberg Foundation, founded by the beer producer
which was an early pioneer in scientific brewing. As Mr. Svensmark puts it
in an online interview in the science magazine Discover:
“We live in a unique time in history, because this period
has the highest solar activity we have had in 1,000 years, and maybe even in
8,000 years. And we know that changes in solar activity have made significant
changes in climate. For instance, we had the little ice age about 300 years ago.
You had very few sunspots between 1650 and 1715, and for example, in Sweden in
1696, it caused the harvest to go wrong. People were starving - 100,000 people
died - and it was very desperate times, all coinciding with this very low solar
activity. The last time we had high solar activity was during the medieval
warming, which was when all of the cathedrals were built in Europe. And if you
go 1,000 years back, you also had high solar activity, and that was when Rome
was at its height. So I think there’s good evidence that these are significant
changes that are happening naturally. If we are talking about the next century,
there might be a human effect on climate change on top of that, but the natural
effect from solar effect will be important.”
Far from all scientists agree that there is an intimate link
between the alleged global warming going on today and cosmic rays, although the
American astrophysicist Eugene Parker, the discoverer of solar wind, takes this
hypothesis seriously. Nevertheless, these investigations contribute to an
emerging multidisciplinary field of cosmoclimatology, the study of how “space
weather” and events outside of the Earth itself may affect the climate on our
planet.
According to NASA’s fine website there are at least 100
billion stars in our own Milky Way Galaxy, possibly much more than that,
compared to a trillion (million times a million) or so in the huge neighboring
Andromeda Galaxy. Our Solar System lies in a spiral arm about 25,000 light-years
from the center of our galaxy and needs approximately 225 million years to
complete one orbit of it. There are some scientists who speculate whether our
position relative to the Milky Way’s center can be associated with
certain geological time periods on Earth.
Scholars
during the past two hundred years have vastly increased our knowledge about the
chemistry of life. European chemists in the early
nineteenth century made a distinction between inorganic and organic chemistry.
They correctly considered the latter to be more complex, but mistakenly believed
that organic substances could only be made by living creatures. This changed
when the gifted German chemist Friedrich Wöhler (1800-1882), a student
of the Swedish scholar Jöns Jakob Berzelius who also collaborated with the leading German
chemist Justus von Liebig, in 1828 discovered that
urea, an organic compound and one of the constituents of urine, could be
synthesized from inorganic materials.
Gradually it
became clear that there is no fundamental difference between organic and
inorganic chemistry apart from the fact that organic compounds are often
complex. They contain carbon atoms, which have the ability to combine with other
atoms in numerous different ways. The German chemist Friedrich August Kekule von Stradonitz, or August Kekulé
(1829-1896), who taught at the Universities of Heidelberg, Ghent and
Bonn, in 1858 established the fact that carbon has a valence (combining
power) of
four. This insight was of fundamental importance in the evolution of organic
chemistry, which is today synonymous with carbon-based chemistry. Kekulé had the
idea that carbon atoms could link up in rings as well as chains. This was
independently proposed by Archibald Scott Couper (1831-1892) from Scotland as
well. In
1865 described the ring structure of benzene molecules.
Carbon with atomic number six has
physical properties which enable it to form millions of compounds. It has two
common allotropes where its atoms are bonded together in different ways:
Diamond is the hardest known naturally occurring mineral while graphite is soft
and was named by Abraham Gottlob Werner from Greek for “to write” due to its use
in pencils.
A more recently discovered class of carbon allotropes are
fullerenes, hollow, cagelike
molecules composed of at least 60 atoms of carbon. Spherical fullerenes resemble a European-style
football and are called “buckyballs” after the American architect Buckminster
“Bucky” Fuller (1895-1983), famous for his geodesic domes. C60 fullerene was discovered in 1985 by a team from Rice University in
the United States and the University of Sussex in Britain. The English chemist Harold Kroto (born 1939) soon shared
a Nobel Prize in Chemistry for the discovery with the Americans Richard
Smalley (1943-2005) and Robert Curl (born 1933). Cylindrical fullerenes are known as
nanotubes and are exceptionally strong.
The Russian biochemist Alexander Oparin (1894-1980) majored in plant physiology at Moscow State
University and was influenced by the ideas of the English naturalist Charles
Darwin. He extended Darwin’s theory of evolution
backwards in time to explain how simple organic and inorganic materials might
have combined into more complex compounds. In 1922
Oparin introduced the concept of a brew of organic compounds and carbon-based molecules, a “primordial
soup,” as the origin of life on
Earth. The English evolutionary biologist J. B. S. Haldane (1892-1964) independently proposed a closely
related, though not entirely identical, hypothesis at roughly the same time.
These ideas initially faced powerful opposition but have since then become
accepted in their main outlines.
Oparin published the book The Origin of
Life and organized the first international meeting on the origin of life in
Moscow in 1957.
The Dutch-born astronomer Gerard Kuiper and the American
physical chemist Harold Urey (1893-1981) renewed interest in the
Solar System. Kuiper discovered the carbon dioxide atmosphere of Mars and
contributed to the first phase of space exploration. Urey investigated the
distribution of elements in the Solar System in his book The Planets: Their
Origin and Development (1952) and helped to develop the field of
cosmochemistry or astrochemistry.
Harold Urey in 1921 entered the University of
California to work under Gilbert Newton
Lewis. He spent the following year at Niels Bohr’s
Institute for Theoretical Physics in Copenhagen, Denmark. In 1931 he developed a
method for distillation of liquid hydrogen which aided the discovery of
deuterium, for which he received a Nobel Prize in 1934. Deuterium is a stable
isotope of hydrogen where the nucleus contains one proton and one neutron.
Tritium is a radioactive and very rare hydrogen isotope with two
neutrons.
Urey moved to Chicago in 1945. One of his doctoral students
at the University of Chicago was Stanley Miller (1930-2007), who decided to
test the Oparin-Haldane theory experimentally. The famous Miller-Urey experiment
from 1953 mixed water, methane, ammonia and hydrogen in a chamber to simulate
the Earth’s presumed early atmosphere and used an electric discharge to simulate
lightning. After just a week, organic compounds had been formed in the shape of
amino acids, the basic building blocks of
life as we know it.
There are those who believe that the oceans appeared as soon as two hundred million years after the Earth
was formed (it was too hot before that), while others think this happened later
and that primitive life forms developed soon afterward, maybe 3.8 billion to 3.5
billion years ago. The oxygen-rich atmosphere we currently enjoy, which makes
complex life forms such as ourselves possible, is the result of several billion
years of work by cyanobacteria, also known as blue-green algae, which use water,
carbon dioxide and sunlight to produce oxygen.
Around the year 1900, several
European scientists rediscovered a neglected research paper on heredity by the
Bohemian monk Gregor Mendel, who had conducted breeding experiments with pea
plants a few decades earlier.
The American geneticist Thomas Hunt Morgan
soon demonstrated that chromosomes are key factors in heredity. DNA had been isolated by the Swiss physician Friedrich Miescher
already in 1869, but he didn’t grasp the importance of his find. In 1944 the Canadian-born USA-based medical
researcher Oswald Avery and his co-workers
more or less demonstrated that DNA itself was the unit of genetic inheritance, a
fact that was further established through experiments conducted by the
Americans Alfred Hershey and Martha Chase in 1952.
Finally, James D. Watson and Francis Crick working at Cambridge University in
England delineated the double-helix structure of DNA in 1953.
DNA,
deoxyribonucleic acid, is the molecule that contains the genetic code for all
currently known life forms on Earth except for some RNA-based viruses. Whether
viruses constitute life forms is debatable since they have no metabolism and
cannot reproduce without infecting a host cell. DNA consists of two long,
twisted chains made up of nucleotides. Each nucleotide contains one base, one
phosphate molecule and the sugar molecule deoxyribose. A gene is
a segment of a DNA molecule that contains information for making a protein.
Proteins perform the chemical reactions in our bodies and provide the body’s
main building materials, forming the architecture of our cells. Amino acids are
the building blocks of proteins. Chromosomes are cellular structures containing
genes. Humans normally have 23 pairs of chromosomes.
During sexual reproduction the egg cell of the mother and
the sperm cell of the father undergo cell division where the 46 chromosomes are
divided in half and the egg and the sperm cells end up with 23 chromosomes each.
The baby ends up with a complete set, half of them from each parent. In every
cell in the human body there is a nucleus where genetic material is stored in
genes grouped in chromosomes. Individuals suffering from the disorder known as
Down’s syndrome, named after the English
doctor John Langdon Down (1828-1896) who first described it in 1866, have three
copies of chromosome number 21. The correct explanation for this was made by the
French geneticist Jérôme Lejeune (1926-1994) in 1959.
Evolutionary biologists differ in their views of what came
first, genes and then proteins or vice versa: this is
the new version of the old chicken or the egg debate. Unlike double-stranded DNA, the related ribonucleic acid (RNA)
usually comes as a single strand and is quite flexible. According to the
website of the National Institute of
General Medical Sciences, “Each year, researchers unlock new secrets about RNA.
These discoveries reveal that it is truly a remarkable molecule and a
multi-talented actor in heredity. Today, many scientists believe that RNA
evolved on the Earth long before DNA did. Researchers hypothesize - obviously,
no one was around to write this down - that RNA was a major participant in the
chemical reactions that ultimately spawned the first signs of life on the
planet.”
One of the most important breakthroughs in biology during
the twentieth century was the realization from the 1970s and 1980s on that life
on our planet is far hardier than scientists had previously suspected. Living
organisms have been found in many extremely harsh and difficult environments
ranging from the superheated waters of submarine volcanic vents to the ultra-dry
bitter cold of the Antarctic Dry Valleys. We can encounter organisms living in
boiling water or caves dripping with sulfuric acid. Most of these extremophiles are
microbes.
The American research vessel Alvin, which in 1964 became the first
deep-sea submersible capable of carrying a pilot and two observers to a depth of
4,000 meters, discovered black smokers in 1977 as it
surveyed the Galapagos Rift in the eastern Pacific Ocean. One of the pioneers
in the field of deep-water research and archaeology is
Robert Ballard (born 1942), an explorer and oceanographer from the
United States. Ballard is perhaps most remembered among the general public for
his discovery of the wreck of the famous RMS Titanic in 1985.
Black smokers are chimneylike structures
on the ocean floor made up of sulfur-bearing minerals or sulfides. Just as we
can find natural hot springs in certain volcanically active regions on land,
similar phenomena called deep-sea hydrothermal (hot water) vents can occur under
the oceans within mid-ocean ridges, where
molten rock bubbles up from the mantle to the sea floor and forms new oceanic
crust. Here we can encounter unusual life forms such as tube worms and giant
clams. Most notably, in this environment of perpetual darkness we can find
entire ecosystems that exist totally without the aid of
sunlight. They are based not on the more common photosynthesis but on
chemosynthesis, by converting heat, methane and sulfur into energy and
food. A few researchers such as the German chemist
Günter Wächtershäuser (born 1938) have suggested that life on Earth may have
begun in similar environments.
Tardigrades, sometimes known as “water bears,” are tiny
water-dwelling eight-legged critters that grow to a size of about 1
millimeter. They are able to survive extreme temperatures and
live from the highest mountain tops to the bottom of the oceans. In
2008 a box of water bears was launched
into orbit aboard the Russian Satellite FOTON-M3 and spent ten days in
containers that exposed them to the vacuum, radiation and extreme cold of space.
Amazingly, some of them survived this brutal treatment and returned to Earth
where they managed to lay healthy eggs. While tiny and simple, tardigrades are
nevertheless multicellular organisms technically classified as animals. This was
the first time that it had been demonstrated that an animal with a mouth, head,
brain, legs, eyes, nerves and muscles has the ability to survive unprotected in
space - an ability previously only proved for some lichens and
bacteria.
A few scientists support the idea of panspermia (“all
seed”), according to which life exist all over the universe, or the more
moderate concept of exogenesis (“outside origin”) where life on Earth originated
elsewhere, maybe in the form of extraterrestrial microbes brought here with
meteorites. These hypotheses are highly controversial and remain the view of a
very small minority of scholars, but the fact that a few microscopic terrestrial
organisms can survive in space is certainly interesting. Since life on our
planet is hardier than we expected this increases the likelihood that it can
exist elsewhere, too. This is especially intriguing now that we finally have the
technological capability to explore other bodies in our Solar System.
The polymath
Mikhail Lomonosov (1711-1765) was a pioneer of modern science in the Russian
Empire. Born in a small village, his family were nominally peasants but still
enjoyed a degree of freedom not known to serfs in Central Russia. He concealed
his identity, as peasants could not attain the prestigious Academy in Moscow,
and pretended to be the son of a priest to gain admission. He soon impressed his
teachers with his intelligence. In 1735 he was selected to the new Imperial
Academy of Sciences in St. Petersburg. Lomonosov studied for several years in
Western Europe and picked up a German wife. In 1748 he opened the first modern
chemical laboratory in Russia. He also promoted Russian history and
language.
According to the book Venus in Transit by Eli Maor,
“It was during the 1761 transit that Lomonosov, observing from his home in St.
Petersburg, saw a faint, luminous ring around Venus’s black image just as it
entered the sun’s face; the sight was repeated at the moment of exit. He
immediately interpreted this as due to an atmosphere around Venus, and he
predicted that it might even be thicker than Earth’s. Lomonosov reported his
finding in a paper which, like most of his written work, was only published many
years after his death in 1765. But it was not until 1910, one hundred and fifty
years after the transit, that his paper appeared in German translation and
became known in the West. Up until then the discovery of Venus’s atmosphere had
been credited to William Herschel.”
The Venera 7 probe from the Soviet Union in 1970 became the
first space probe to transmit data from the surface of Venus. The Earth’s
atmosphere is by volume composed of roughly 78% nitrogen gas (N2), 21% oxygen gas (O2), 0.9% argon (Ar), some water
vapor (the gas phase of water, H2O), almost
0.04% carbon dioxide (CO2) and small amounts of a number of other
gases such as methane (CH4). While the three
latter gases constitute a tiny part of the atmosphere they trap heat from the
Sun and warm the Earth through the greenhouse effect.
The mass of the atmosphere of Venus consist of 96.5% carbon dioxide and
the planet is surrounded by thick clouds of sulfuric acid. The dense atmosphere produces a run-away greenhouse effect and the temperature of Venus’ surface is more than 460 degrees
Celsius, hot enough to melt lead. It is highly unlikely whether life as we can
conceive of it can exist in such an inhospitable environment, except possibly in
the cooler upper atmosphere. The Martian atmosphere, too, is dominated by carbon
dioxide at 95.3 percent plus some additional nitrogen, argon and water vapor,
but at the surface the atmospheric pressure is typically 0.7 percent that of the
Earth’s surface. In contrast, atmospheric pressure at the surface of Venus is
about 92 times that of the Earth and by extension roughly ten thousand times
that of Mars.
The astronomer Giovanni Schiaparelli (1835-1910) from the winy
Piedmont region of northwestern Italy explained regular meteor showers as the result of the dissolution of
comets and proved it for the Perseids, thereby forging a
link between comets and certain meteors. He studied Mars
and named its “seas” and “continents.” According to the book The Planet Mars: A History of Observation and
Discovery by William Sheehan, “In Italian,
canali can mean either ‘channels’ or ‘canals.’ It is clear that
Schiaparelli had completely natural features in mind---indeed, he often used the
word fiume (river) as a synonym. Strictly speaking, the term
channel would have been preferable, but instead it was canal, with
all its connotations of artificial waterways, that was adopted in English, with
far-reaching consequences.”
Schiaparelli’s alleged observations of Martian canals stimulated the American
businessman and astronomer Percival Lowell (1855-1916) to found his observatory
in the 1890s and search for intelligent life on Mars.
He also predicted the existence of a planet beyond the
orbit of Neptune. The young American astronomer Clyde Tombaugh (1906-1997)
discovered Pluto in 1930 while working at the Lowell Observatory in the USA. He
used photographic plates, which were used in astronomy and particle physics long
after they had gone out of popular use, although astronomers like many others
later switched to digital cameras. In Roman mythology Pluto, the equivalent of the Greek deity
Hades and his abode of the same name, was the god of the dark underworld. “PL”
also happens to be the initials of Percival Lowell.
Our seasons are caused by the Earth
being tilted on its axis by 23.5 degrees. This
axial tilt is not constant but varies very slowly from 22.1 to 24.5 degrees in a
cycle of 41,000 years. In June the Northern Hemisphere faces the Sun and
receives more direct sunlight, which means that there is summer in the north and
winter in the Southern Hemisphere. The exact opposite is the case six months
later when the Earth is on the other side of its orbit and is tilted the other
way vis-à-vis the Sun. The seasonal daylight differences and the
gradual lengthening or shortening of days are subtle in the tropics, but the
regions next to the poles will be in total darkness by mid-winter and in turn
receive 24 hours of nonstop sunlight (the “midnight Sun”) in the middle of the
summer, close to winter solstice and summer solstice,
respectively.
Mars has an axial tilt of 25.2 degrees and has seasons just
like the Earth, only longer ones since the Martian year - its orbital period
around the Sun - is longer with 687 Earth days. One crucial difference is that
while the Earth’s orbit is nearly circular, Mars has a significantly more
elliptical orbit with a more pronounced orbital eccentricity. This means that
the difference between the point when it is closest to the Sun, the
perihelion, and the point when it is furthest away from the Sun, the
aphelion, is small and climatically insignificant for our own planet but
significant in the case of Mars. While the Martian atmosphere is thin it is
still dense enough to support a weather system. Huge dust storms can cover
almost the entire planet and are often strongest at perihelion when the Sun
heats its atmosphere the most.
Mars is named for the ancient Roman god
of war. Its reddish color, similar to that of rust (iron oxide), comes from
iron-rich minerals in its soil. Large amounts of water probably once flowed on
its surface, which contains many channels, gullies and huge valleys. The
planet’s seasonal polar caps consist of a mixture of solid carbon dioxide (“dry
ice”) and water ice.
Since there are currently no seas on Mars there is no “sea
level” to measure from, but by any standard the massive shield volcano Olympus Mons is the largest known mountain in the
entire Solar System. Standing about 25 kilometers higher than its surrounding
landscape it is almost three times higher than Mount Everest. However,
the force of gravity at the Martian surface is only about 38 percent that
of the Earth. A mountain of similar size probably wouldn’t have survived on our
planet as it would have been crushed under its own weight.
While it remains a possibility that plate tectonics once
existed on Mars, astrogeologists believe that plate tectonics processes
are no longer active there. Olympus Mons is thought to be fixed over a deep
hotspot, which has allowed repeated eruptions to build it to its present height.
On the Earth, hotspots remain stationary while crustal plates are
moving above them. It is virtually certain that our hot sister planet Venus is
still volcanically active. It is distinctly possible that cooler Mars is so as
well, but we currently possess no direct evidence of this.
Mars has no global magnetic field, which means that its core
is probably entirely solid. The Earth’s magnetic field creates a protective
bubble against the solar wind and harmful rays from space. Since Mars lacks this
and has a thinner atmosphere, the planet’s surface is much more exposed to
potentially harmful radiation. The average temperature is about -60 degrees
Celsius, but varies considerably seasonally and regionally from a comfortable 20
degrees plus near the equator at summer to a staggering minus 130 degrees
Celsius near the poles during the winter. Because of these factors, if evidence
of past or present microbial life is ever found on Mars, many astrobiologists
suspect that it will be located just below the surface. There, microbes might be
more shielded from cosmic radiation, and heat from the still hot Martian core
makes it more likely that non-trivial amounts of water could still exist in
liquid form.
Joan Oró
Florensa (1923-2004) was a
Catalan biochemist who graduated from Barcelona University in 1947 and emigrated
from Spain to the USA in 1952. Following the Miller-Urey experiment from 1953,
Joan Oró in 1959 demonstrated in
a related experiment that adenine, one of the components of DNA, formed in
abundance in his “primordial soup.” Oró was one of the first scientists to
suggest the possibility that comets could have acted as carriers of organic
molecules to the Earth’s early biosphere. From the 1960s he worked with NASA,
including the Viking missions to Mars in 1976. While the results were
inconclusive back then, it is possible that their equipment was not sensitive
enough to detect life forms even if present.In 2003-2004,
American space scientists as well as data from the Mars Express Orbiter by the
European Space Agency (ESA) found evidence of methane in the Martian
atmosphere. There could be an active source of methane production on the planet.
This is not by itself proof of the presence of life as methane can be produced
through both biological and non-biological processes, but the discovery is
definitely encouraging. Obviously, if we do find extraterrestrial life on
Mars or elsewhere it is not at all certain that it will be carbon-based and
DNA-based as life is on our own planet. Theoretically speaking, extraterrestrial life
could be so different from the life forms we are familiar with that we would
find it hard to recognize it as life at all.
From the Age
of Exploration until the twentieth century, European explorers and eventually
scholars reached almost all corners of the planet, including the polar region.
Vitus
Bering (1681-1741), a Danish navigator in the service of the Russian Navy, was
the first known European to see Alaska. The Bering Strait, which separates
Siberia and the Asian continent from North America, is named after him. Across
this strait there was a land bridge during the last Ice Age. It is likely that
nomadic hunters from Siberia entered Alaska and the Americas from here. There is
archaeological evidence of the widespread presence of the Clovis culture in
North and South America before 10,000 BC, but it is remains possible that there
were several different waves of settlement and that the first one began even
earlier than this.
The
expeditions of the American explorers Frederick Cook (1865-1940) and Robert
Peary (1856-1920) to the North Pole region and those of the Norwegian explorer
Roald Amundsen (1872-1928) and the Anglo-Irish explorer Ernest Shackleton
(1874-1922) to Antarctica, while greatly fascinating, were not noted primarily
for their scientific interest; they were more about glory and adventure in
addition to the possibility of discovering new and potentially important sea
lanes. Modern polar science began with the first International Polar Year in
1882. This was the brainchild of the officer Carl
Weyprecht
(1838-1881) of the Austro-Hungarian navy,
who had discovered Franz Josef Land in 1874 while searching for the Northeast
Passage.
Expeditions to
Greenland by the Norwegian explorer and scientist Fridtjof Nansen (1861-1930) in
the 1890s and by Alfred Wegener from Germany in the early 1900s surveyed the
glaciers and ice sheets there. The same was the case with the British Royal Naval
officer
Robert
Falcon Scott’s (1868-1912) Antarctic expedition of
1901-1904. In recent decades, ice sheets have gained international attention for
preserving some of the finest records of climate change over the last hundred
thousand years or more. Glaciology, the study of ice, ice
formations and glaciers, is also of major importance to planetary
scientists.
>Next to Mars,
the most promising candidates for primitive life in our Solar System might not
be the planets but rather some of their moons. The study of ice on
bodies such as Jupiter’s moons Europa, Callisto and Ganymede as well as
Saturn’s icy satellites Enceladus with its large
water vapor geysers and especially Titan with its dense atmosphere and surface
liquid in the form of hydrocarbon lakes is an emerging
scientific field. Ganymede is the largest
satellite in the Solar System. Like Titan it is larger in diameter than the
innermost planet Mercury but has less mass. Mercury is a dense object.
Europa may
harbor a liquid water ocean and is therefore a priority target for future space
probes. The same could be true of Callisto.
The fourth of
Jupiter’s large Galilean moons, Io, is the most volcanically active body in the
Solar System, with volcanoes spewing out sulfur and sulfur dioxide to a height
of hundreds of kilometers. The heat is caused by massive tidal forces generated
by Jupiter and other moons. Volcanism exists on several bodies, though not
necessarily in the form of molten rock (lava) as we can see here on Earth.
The path-breaking American Voyager 2 spacecraft in 1989 observed
cryovolcanoes (ice volcanoes) on Triton, the largest moon of
the planet Neptune. The temperature at the surface of Triton is only 34.5 K
(-235 C), at least as cold as Pluto. In this extreme cold methane, nitrogen and
carbon dioxide all freeze solid. The geysers Voyager 2 observed on Triton are
probably nitrogen geysers driven by seasonal heating by the Sun.
A recent
advance of tremendous importance is the discovery of the first extrasolar
planets, planets orbiting other stars. Hundreds of these have been found during
the first generation after 1990 alone. This has led to the establishment of a
new branch within planetary science dubbed exoplanetology or exoplanet science.
Most of the planets discovered so far have been gas giants detected through
indirect means by observing the effects they have on the stars they orbit, but
methods are rapidly improving and more Earth-like planets have been
identified.
It is highly
unlikely that we in the foreseeable future, if ever, will have the technological
capability to send robotic probes to explore extrasolar planets, let alone
manned missions. Nevertheless, by studying them from a distance we can learn a
great deal about planet formation and about how common Earth-like planets are in
our galaxy and in the universe.
Unlike most elements lighter than iron the alkali metal
lithium with atomic number three is not easily produced in stars. According to
current theories, most of it was probably created after the Big Bang. Yet
astronomers see a wide range of different lithium levels in Sun-like stars. With
the European Southern Observatory’s HARPS spectrograph survey of hundreds of
stars, astronomer Garik Israelian of Spain's Instituto de
Astrofisica de Canarias in Tenerife and his colleagues found that those that had
an orbiting planetary system had lithium levels similar to the Sun’s while those
that did not had higher levels. If this insight is correct it might suggest an
easier way to look for undiscovered planetary systems around other
stars.
