Archive | March, 2014

Mechanical gears in Nature

26 Mar

The Issus is a plant-hopping insect living in gardens all across Europe (Fig.1). Now, scientists found they have in their legs gear mechanisms previously thought to be man-made and used on every bicycle and car gear-box. Their discoverers from the University of Cambridge said that this is the “first observation of mechanical gearing in a biological structure”, and published their findings in the journal Science.

As it is clearly seen on Fig.2, the gear teeth on the opposing hind-legs lock together. The legs move within 30 microsecond of each other, securing complete synchronicity in leg movement, otherwise would result in “yaw rotation” and putting the insect spinning out of control.
It is hard to understand how random mutation could provide the Issus with a so complex and perfect mechanism, but the authors said: “These gears are not designed; they are evolved – representing high-speed and precision machinery evolved for synchronisation in the animal world.”  It is worth to mention that the mechanistic gears are only found in the insect’s juvenile – or ‘nymph’ – stages; they are lost in adulthood. The authors apparently suggest that the risk of breaking one tooth on the gear due to systematic use (entropy!) may be the reason why nature prefers another solution.

 

Fig. 1 – The Issus. Image credit: Cambridge University.

 

Fig. 2 - Gears inside the Issus. Image credit: Cambridge University

Fig. 2 – Gears inside the Issus. Image credit: Cambridge University

REF.
{1} – Site Cambridge University

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Mars

22 Mar


Come my friend

‘Tis not too late to seek a newer world-

Alfred, Lord Tennyson”

Mars is on the mind of scientists for the reason addressed by Lord Tennyson. There is noticeable differences between Earth and Mars. The Earth’s crust is formed by tectonic plates that move slowly, driven by convection currents in the molten core. But on Mars there are no tectonic plates. The surface of Mars is shaped by volcanoes, cratering and vast magma upheavals similar to the ones that created The Tharsis bulge and the Valley Marinensis (Fig.1). Mars has the largest volcano in the Solar system: Olympus Mons, covering na área 600 km in diameter and 27 km high.

800px-Tharsis_-_Valles_Marineris_MOLA_shaded_colorized_zoom_32

The Tharsis region. Image credit: Wikipedia.

A martian day is only 3 % longer than Earth’s day, while the year is equivalent to 687 Earth’s day. Due to its eccentricity (the most one after Pluto), see Fig.2, the solar input varies significantly during the martian year.

Mars eccentricity is higher than Earth. Image credit: http://www.windows2universe.org/mars

Mars eccentricity is higher than Earth. Image credit: http://www.windows2universe.org/mars

There is water in vapour form in the atmosphere and in the ice caps at poles; evidence exists that water in liquid form was present before on Mars. Probably due to Mars eccentricity the southern hemisphere has very little water vapor (0 to 0.3 precipitable micrometer, but in contrast the northern hemisphere shows a significant amount of water (up to 75 micrometers at 70-80 ^o N). On the basis of the abundance of water vapor in the polar region, an estimate of the lower limit on the atmospheric temperature can be given, being about 205 K (or -68 ^oC). This is an indication that the permanente polar cap is made of water ice (confirmed by Viking spacecraft) with a tickness between 1 meter and 1 kilometer. The atmosphere contains concentrations of nitrogen, árgon, carbon dioxide, molecular oxygen, atomic oxygen, and nitric oxide that are detectable. However, the thiness of the Martian atmosphere was disappointing, with a value one-tenth of Earth’s. According to Anders and Owen, five processes working in combination may have been responsible for the thin atmosphere: i) a small endowment of volatiles gases; ii) incomplete outgassing from the interior; iii) recondensation or trapping in surfasse regions; iv) catostrophic loss of the early atmosphere; v) gradual escape of the lighter constituents.

Olympus mons on Mars. Image credit: http://annesastronomynews

Olympus mons on Mars. Image credit: http://annesastronomynews

But this situation results, too, because Mars has only half Earth’s diameter, 11% its mass and 38% its gravity, increasing the probability of gas escape at the upper layers of the original atmosphere.

The gravity on Mars is lower than on Earth; a person weighing 100 kg on our planet would have 38 kg on the surface of Mars…

See this wonderful movie prepared by NASA showing the intricacies of a mission to the Red Planet. Astounding!

REF:
[1] – Expedition Mars, by Martin J.L. Turner

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