Monthly Archives: August 2012
As you know, these days Mars is back in fashion. On August 6th, we have seen the Mars Science Laboratory (MSL) of the NASA  landing successfully on the red planet, and now the Curiosity rover is walking to see what is there. This robot of about 900 kg, the largest that has been managed to land safely on Mars, is very well equipped. It contains 10 scientific instruments, including infrared laser teledetector, mass spectrometer, gas chromatograph, X-ray diffraction, microscopic camera, radiation detector, weather stations, and more than 17 photographic cameras .
These equipments are designed to detect any trace of water, to analyze accurately the rocks, to study the minerals in the Martian surface, to measure the chirality of the molecules detected (you know, L-or D-, such as L-amino acids typical of living beings) and to take pictures in high resolution.
The Curiosity rover, of Mars Science Laboratory mission, NASA
With these tools, the main objective of the MSL is determining whether there have been conditions conducive to life in Mars. Therefore, rather than looking directly for finding living beings, the goal is to try to find if there are any signs of past or present life, and also for looking the possibilities for a possible human settlement.
Life as we know it on Earth is based on the chemical elements of the basic biochemistry, namely carbon, oxygen, hydrogen, nitrogen, phosphorous, sulphur, and other trace elements. While these elements are found in many parts of the outer space, including Mars, it is necessary to quantify them to see if their proportions are indicative of a possible life, present or past, on Mars.
Of course, a key point in the search for life is to find liquid water, since on Earth there are living beings wherever there is liquid water, regardless of other conditions, aerobic or not, and extreme pHs and other inhospitable conditions. As you know, there are organisms on Earth everywhere, and among the so called extremophiles, either archaea or bacteria, there are some living at sea depths with enormous pressures, some others living at pH below 1 and temperatures near the boiling point, others a few hundred meters underground, others in the upper atmosphere, others endure radiation, others in a high osmotic pressure (e.g. saline environments). But in all cases, and even sometimes with very few nutrients, organisms live always in the presence of liquid water, even at low concentration. On Earth, wherever there is liquid water, always living beings are found, mainly microorganisms.
So well, is there liquid water in Mars ? It seems highly unlikely, but not impossible at all. There is water, certainly, especially ice at the poles (see picture) and in other places, but the low atmospheric pressure (the highest on the Martian surface is 0.6% of the Earth’s one), makes ice sublimating directly to water vapour, which is hardly retained by the atmosphere and escapes the planet. The Martian atmosphere contains 95% CO2, 3% N2, and traces of oxygen and water, as well as many particles in suspension. These give a tawny colour to the atmosphere, similar to the aspect of the planet as we see, due to abundance of iron oxide. Surface temperatures oscillate from about -140 °C at the poles to about 35 °C, occasionally at the equator. Therefore, even temporarily, there can be liquid water.
True-colour view of Mars seen through NASA’s Hubble Space Telescope
Despite the current hostile conditions of Mars, there is geological evidence of the existence of liquid water in the past, like the geomorphology of valleys and channels, etc., and also by the presence of some minerals that only can be originated with water (e.g. hematite).
On the other hand, small amounts of methane and formaldehyde have been detected there. These compounds are mostly generated biologically on Earth, but conditions of the Martian atmosphere make them short-lived . However, their geological origin seems also possible.
The habitability of Mars has been tested in the laboratory reproducing its conditions, by placing polar and alpine lichens at these conditions . Surprisingly, it has been shown that these lichens can resist them.
The question of possible life on Mars had a peak in 1996, when scientific staff from NASA published in Science magazine  the microscopic images of a fragment of ALH84001, a meteorite from Mars. This stone seems to be of Martian origin, it was launched into space by the impact of a meteorite on Mars about 15 million years ago, and then it travelled till the Earth reaching the Antarctica, where it was found in 1984. The structures seen there recall bacterial chains, and so, it was proposed that they would be martian microfossils. However, there is no other evidence of the biological origin of these structures and afterwards an inorganic origin of the meteorite minerals has been proposed .
Electronic microscopy of a fragment of ALH84001 meteorit (image of NASA)
Well, we wait with expectation the results of the tests done by the Curiosity. If evidence of past or present life on Mars is found, there will be very much to think about, especially in the sense that terrestrial organisms would not be alone in the universe. And in spite of the evidence that would be very simple microbial life, we should conclude that life is a feature very widespread in the universe.
What do you think ? Will Curiosity find evidence of life on Mars ?
Earth and Mars, at the same scale, two Bio-planets ? (image from NASA)
 NASA: http://www.nasa.gov/mission_pages/msl/
 Mahaffy, P. (2009) Sample analysis at Mars: Developing analytical tools to search for a habitable environment on the red planet. Geochemical News (Geochemical Society), 141, oct. 2009
 Krasnopolski, V.A. et al. (2004). Detection of methane in the Martian atmosphere: evidence for life?”. Icarus 172, 537–547
 DLR (German Aerospace Center) Surviving the conditions on Mars: http://www.dlr.de/dlr/en/desktopdefault.aspx/tabid-10081/151_read-3409/
 McKay, D.S. et al. (1996) Search for past life on Mars: Possible relic biogenic activity in Martian meteorite ALH84001. Science 273, 924–930
 Golden, D.C. et al. (2004) Evidence for exclusively inorganic formation of magnetite in Martian meteorite ALH84001. American Mineralogist 89, 681–695
[ ] … and Wikipedia:
– Mars Science Laboratory: http://en.wikipedia.org/wiki/Mars_Science_Laboratory
It is the “pearl of Siberia”, so named for its beauty and nature. As shown on the map below, it is located in the south of central Siberia, in the Russian Federation, quite near of Mongolia and China. Historically, the chinese called it as the North Sea. The Russians do not began to explore the lake until the end of 17th century. Although today most of the population is of russian origin, the south of the lake is inhabited by buryats, of Mongolian origin. They are the largest ethnic minority group in Siberia, with their own language. They are about 400,000 and their principal city is Ulan-Ude.
The famous Trans-Siberian railway passes beside the lake, bordering it by the southwest corner, with stops in the cities of Irkutsk and Ulan-Ude. This section is spectacular, with 200 bridges and 33 tunnels. This area is “only” about 5000 km far from Moscow (3 days) and 4000 km of Vladivostok (3 days) in the Pacific.
As you can see in this map, the lake is shaped like a crescent. It is the largest freshwater lake by volume in the world (23,600 km3), it contains more water than the North American Great Lakes combined, although it is not the largest by surface (31,000 km2), due to because it is the deepest (1600 m maximum depth). It is aldo the world’s oldest (about 25-30 million years ago). The lake is in a rift, where tectonic plates are separating, and so it widens gradually.
It has an enormous biodiversity, with over 1700 species of plants and animals, 2/3 of which are endemic, and in 1996 UNESCO declared it a World Heritage Site. With minimum temperatures of -20°C most of the winter, lake Baikal is frozen for half the year.
The Baikal seal
The Baikal seal or “nerpa” is Pusa sibirica (formerly classified as Phoca sibirina), which is across all the lake, but nowhere else. The lake is 2400 km far from the Arctic ocean where the lake waters flow through the siberian river Yenissei.
The nerpa is one of the few species of freshwater seals. It is relatively small, measuring just over 1 meter and weighs about 60-70 kg. It eats several species of fish, but especially a so-called “golomyanka”, which is endemic of lake Baikal. This fish is very abundant in the lake, it is translucent, very fat (it is known as “oilfish”) and lives at depths of 200-500 meters. Seals dive down to eat them, they can resist up to 40 minutes underwater.
Well relaxed Baikal seals. Picture from Uryah. http://diertjevandedag.classy.be/zoogdieren/roofdieren/zeehond/baikalrob.htm
Well, and how this seal came to lake Baikal ?
Well, it is not very clear, it is almost a mystery, since the seal lives far from the open seas, where all other species of seals live. But anyway, as for everything, we can look for the more reliable scientific hypothesis. Let’s see what we can found ….
This species is most similar to the Arctic seal or ringed seal, Pusa hispida, which lives in the Arctic. Like this and other of the family of Phocids (such as the common seal, Phoca vitulina), it is earless, unlike other Pinnipedia (sea lions and fur seals). Another species quite similar is the Caspian seal, Pusa caspica, which is also a curious case, because the Caspian is also an isolated sea. But the Caspian is almost a real sea, with a salinity of 1.2% (the third of the others seas and oceans), and therefore the Caspian seal, such as the Arctic, is not a freshwater seal.
However, there are two subspecies of the arctic seal, with few numbers, which are freshwater, like that of Baikal lake: they are the seals of lakes Saimaa (Finland) and Ladoga (Russia, near Finland), which are relatively near of the Arctic ocean. These two subspecies probably came from the Arctic, after the last glaciation, and they remained confined to these lakes. Probably, to change from salt water to freshwater is a relatively easy adaptation for mammals like these.
Another common feature of the Baikal seal and these of the same genus Pusa (the arctic and the Caspian ones), and others, is that their pups have white fur, changing it shortly after to the grey fur typical of adults. This suggests the origin of the common ancestor in a icy place, the arctic or a related environment.
Therefore, the prevailing scientific theory by 1960  was that the origin of Baikal and Caspian seals from the Arctic would have been during one of the glacial periods of the Pleistocene, perhaps around 90,000 years ago, that is relatively recent in terms of evolution. As shown in the map below, during this period, north ice of the arctic covered part of Siberia (red line) and functioned as a barrier to all waters coming from the south, which currently drain to the Arctic ocean (by the rivers Ob and Yenissei, and others). Thus, a large lake was formed, which communicated probably with the Baikal and the Caspian, and all water flowed westward towards the Black Sea, as shown. Geologically, these connections of the Aral and Caspian to the Black Sea seem demonstrated [3, 4]. With this, the seals of the Arctic would have migrated south and led to the Caspian, and the Baikal perhaps.
Map collage of this from Mangerud  (left) with the one of freeworldmaps.net (right). The area in white until the red line was covered by north ice sheet, by 90,000 years ago.
But, as I mentioned, 90,000 years is a very short evolutionary time to explain the differences between these species, although they are closely related.
Therefore, it seems likely a previous common origin, and to prove it, molecular tools have been used the recent years. In this way, specific gene sequences of 12 mitochondrial proteins from different species have been compared. This study has been done including all pinnipeds .
Thus, in developing the corresponding dendrogram, as we see below, it can be observed that the evolutionary separation of the Baikal seal from the Arctic (ringed seal), and the Caspian, and the grey seal, occurred about 5 million years ago, at the beginning of the Pliocene. Therefore, these species of seals must have a common geographical origin, relating to these arctic lakes or internal seas. Molecular similarities have been also found between arctic amphipods (small crustaceans) and those of the Caspian Sea.
Furthermore, at the period when this seal speciation took place, and from the Oligocene (20 million years) to the Pliocene, the sea Paratethys (see diagram below) was extending from central Europe to this part Asia, over the Alps, Carpathians and other mountain ranges separating Paratethys from the Tethys sea. In fact, the current Black, Caspian and Aral seas, and other lakes in central Asia, are relics of what was the Paratethys. This great sea had connections with the Arctic during different periods.
Diagram from Woudloper: http://commons.wikimedia.org/wiki/User:Woudloper
Therefore, it is likely that the Caspian seal was originated from the Arctic ones or backwards, through these geographical connections of the Paratethys until the Pliocene. However, for our protagonist, the Baikal seal, there is not enough evidence to say that the Baikal was connected to the other seas of Paratethys because it is quite to the east. So, either Pusa sibirica came across this alleged connection with Paratethys, or maybe there was a separate settlement from the Arctic across the river Yenissei, also at this period. Nothing is discarded. Therefore, the Baikal seal will keep some mystery ……
 Arnason U. et al (2006) Pinniped phylogeny and a new hypothesis for their origin and dispersal. Molecular Phylogenetics and Evolution 41, 345-354
 McLaren I.A. (1960) On the origin of the Caspian and Baikal seals and the paleoclimatological implication. American Journal of Science 258, 47-64
 Mangerud J. et al. (2004) Ice-dammed lakes and rerouting of the drainage of northern Eurasia during the Last Glaciation. Quaternary Science Reviews 23, 1313-1332
 Mangerud J. et al. (2001) Huge ice-age lakes in Russia. Journal of Quaternary Science 16, 773-777
 ……. and Wikipedia, of course !!
Welcome to my blog !
My idea is to write things related to life sciences, that is, biology, my area. For this reason I call the blog BIOS, meaning life in old greek. I mostly will discuss things related to various news related with biology, collecting information from different sites, and adding my humble point of view.
Maybe I will write also about other things that are not so “Bios” because at the end, everything is “life”, right?
Thanks if you read these comments and see you soon.