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Sapphire is a gemstone variety of the aluminum oxide mineral corundum (Al2O3). It often has a blue color (the Greek word sappheiros translates to ‘blue stone’ in English), which is the result of the incorporation of trace amounts of iron in the mineral structure. Sapphire is a precious stone commonly used in jewelry, together with ruby, emerald and diamond.
Information source: Mindat.org
Image: Sapphire crystals found in Pakistan. Source: Parent Géry, Wikimedia Commons.
Research of biologists published in Global Change Biology indicates that emperor penguins on Antarctica were forced into refugia by extreme cold during the last glacial maximum (~ 19.5 – 16 thousand years ago). By comparing the DNA of fossil emperor penguins with the DNA of living individuals and colonies, the scientists were able to reconstruct the population dynamics of emperor penguins on Antarctica through time. Their results show three mitochondrial clades within emperor penguins at the time of the last glacial maximum, which suggests that these birds were isolated in three small, separate populations and may have survived in refugia such as the Ross Sea. The population sizes of emperor penguins are related to the balance between sea ice available for breeding and open water available for foraging. Sea ice extent around Antarctica was much greater during the last glacial maximum than at present and therefore, reduced food availability resulted in severe losses among populations of emperor penguins.
Journal reference: Younger, J. L., Clucas, G. V., Kooyman, G., Wienecke, B., Rogers, A. D., Trathan, P. N., … & Miller, K. J. (2015). Too much of a good thing: sea ice extent may have forced emperor penguins into refugia during the last glacial maximum. Global change biology, 21(6), 2215-2226.
Image: Emperor penguin colony foraging along the Weddell Sea, Antarctica. Source: Christopher Michel, Wikimedia Commons.
Cheetahs (Acinonyx jubatus) are the fastest land mammals on Earth and live in the open grasslands of most parts of sub-Saharan Africa and Iran. They are characterized by a golden fur covered with small, black spots and prey on smaller herbivores such as antelopes and hares. Because of their light and agile build, cheetahs are able to accelerate from 0 km/h to 100 km/h in 3 seconds and run at incredible speeds of up to 120 km/h over short distances. Chasing prey costs massive amounts of energy and requires so much of their bodies that cheetahs even risk brain damage at the end of a chase. As a result, they have to rest and recover in the shadow after each endeavor, during which they are mostly unable to defend themselves or their prey against other predators. Male cheetahs are often social and may live in groups to establish a territory and even hunt together, but female cheetahs are mostly solitary and hunt alone. Females raise their cubs on their own and leave them behind once the young become independent of their mother. Subsequently, female cubs leave the litter as well, but male cubs may remain together for the rest of their lives.
Information sources: National Geographic, WWF
Image: Cheetah in the savanna grasslands of Serengeti National Park, Tanzania. Credit: Tobias, Wikimedia Commons.
The Moon is the celestial body that orbits the Earth. It has a mean radius of ~ 1737 km, a mean distance to Earth of ~ 385 thousand km and an orbital period of ~ 27.3 days. Earth’s satellite is thought to have formed approximately 4.5 billion years ago as a result of the impact between the proto-Earth and a celestial body called Theia, not long after the formation of the Solar System. The Moon has a differentiated structure and consists of a crust, mantle and core and its surface is scarred with many impact craters.
Information source: NASA
Image: Full Moon as seen from Earth. Credit: Gregory H. Revera, Wikimedia Commons.
Earth is the largest terrestrial planet in the Solar System, the third planet from the Sun and the only astronomical object known to sustain life. It has a mean radius of ~ 6371 km, a mean distance to the Sun of ~ 150 million km and an orbital period of ~ 365 days. Earth is thought to have formed approximately 4.55 billion years ago and has one natural satellite, the Moon. The planet has a differentiated structure consisting of a crust, mantle and core and features plate tectonics. Importantly, Earth harbors abundant liquid water at its surface, most of which can be found in its oceans. The planet is surrounded by an atmosphere that contains ~ 78 % nitrogen (N2), ~ 21 % oxygen (O2) and several other trace gases, including carbon dioxide (CO2) and water vapor (H2O).
Information source: NASA
Image: Earth as seen from space, also known as the Blue Marble. Credit: NASA/NOAA/Reto Stöckli.
The Pillars of Creation are pillars of interstellar gas and dust in the Eagle Nebula, ~ 5 lightyears tall and at a distance of ~ 7000 lightyears from the Earth. Massive new stars are being formed within the pillars, but at the same time the gas and dust are being eroded by the intense ultraviolet light from nearby young stars. The different colors in the Pillars of Creation result from the electromagnetic emission from different elements: blue is related to oxygen, orange is related to sulfur and green is related to both hydrogen and nitrogen.
Information source: NASA
Image: The Pillars of Creation in the Eagle Nebula as seen from the Hubble Space Telescope. Source: NASA/ESA/Hubble Heritage Team.
African lions (Panthera leo) are apex predators that live in the barren savanna grasslands of most parts of sub-Saharan Africa, blending in well with the surroundings because of their golden fur. They feed on large herbivores such as wildebeest, zebras, buffalo, warthogs and gazelles, as well as smaller rodents. Lions are the only cats that live together in groups, called prides, which may consist of up to three males, ten lionesses and their young. They rest for most of the day, but are generally active at dusk and during the night. Male lions are known for their long manes and defend the territory of the pride against rivals, while the lionesses are the main hunters and stalk their prey in groups before closing in for a kill. As they grow, young males leave the pride to establish their own, while females often stay behind. Historically, the lion has been regarded as the king of beasts and is therefore still used as a symbol of courage, strength and royalty.
Information sources: National Geographic, WWF
Image: African lions feeding on a buffalo carcass in Kruger National Park, South Africa. Source: Luca Galuzzi, Wikimedia Commons.
Tropical cyclones are massive storm systems that may generate strong winds and heavy rain, as well as high waves, storm surges and even tornadoes. They are characterized by a low-pressure center, called the eye, around which thunderstorms rotate rapidly and spiral outward. Tropical cyclones originate over warm oceans and seas, where the evaporation of large amounts of water creates a vast energy source for storms. Colossal rain clouds form as the hot, moist air rises up in the atmosphere, cools and becomes saturated with water, while the strong rotating winds result from the conservation of angular momentum as the air flows towards the eye of the storm. Together, these processes result in an intense atmospheric circulation system that may continue to grow in size and strength under the right conditions. Tropical cyclones may also be classified as hurricanes or typhoons, depending on their strength and location.
Information source: Encyclopaedia Brittannica, Wikipedia
Image: Cyclone Catarina above the South Atlantic as seen from ISS on March 26, 2004. Credit: NASA.
The Matterhorn is an iconic mountain peak in the Swiss Alps whose summit reaches a height of 4478 meters. The base and lower part of the mountain consist of successive layers of ophiolites and sedimentary rocks, whereas the rocks of the upper part consist of a series of gneisses.
Information source: Encyclopaedia Brittannica, Wikipedia
Image: The Matterhorn in the Alps, Switzerland. Credit: Zacharie Grossen, Wikimedia Commons.
The Mont Blanc is the highest mountain peak in the Alps with a summit that rises up to 4810 meters on the borders between France, Italy and Switzerland. The mountain is always covered in snow and ice and is surrounded by several shoulder peaks, including the Dôme du Goûter, Mont Maudit and Mont Blanc du Tacul. The Glacier du Geant flows down from the slopes of the mountain and feeds into the Mer de Glace, the longest glacier in France.
Information source: Encyclopaedia Brittannica, Wikipedia
Image: Summit of Dôme du Goûter and Mont Blanc in the Alps, France. Credit: Alexandre Bruisse, Wikimedia Commons.
