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3 Most Likely Places for Alien Life in the Solar System

Europa Many would grant Europa a higher potential-life rating than I have, since there’s probably more liquid water here than in all of Earth’s oceans. The downside is that Europa’s vast, salty seas lie beneath roughly 10 miles of ice. Not only is it difficult get a probe beneath this icy armor, but Europa’s oceans are darker than a cave — which means photosynthesis won’t work. However, something down there may subsist on geothermal heat or complex molecules from the surface. Europa possesses a mean radius of 970 miles (1,560.8 km).

Venus A surprise entry in the exobiology sweepstakes is our sister planet, Venus, with its scorching surface temperatures (850 F, or 454 C). The planet is generally assumed to be as sterile as a boiled mule.

But planetary scientist David Grinspoon, astrobiology curator at the Denver Museum of Nature and Science, points out that high in the Venusian atmosphere temperatures are refreshingly tolerable. Atmospheric sulfur dioxide and carbon monoxide might serve as food for floating microbes. Venus is 7,521 miles wide (12,104 km). 

Callisto and Ganymede I considered these two moons of Jupiter together, as I feel they’re neck-and-neck candidates for biology. Like their more celebrated neighbor Europa, Ganymede and Callistomay have buried, liquid oceans. However, in the case of these two satellite siblings, briny deeps would underlie at least 60 miles (100 km) of rock. Finding inhabitants here is a shovel-ready project for our grandkids. Callisto has a diameter of more than 2,985 miles (4,800 km); Ganymede’s diameter is 3,270 miles (5,262.4 km).

A study shows that Traces of water in moon came from Earth.

Traces of water inside the moon were inherited from ancient Earth, according to a fresh analysis of lunar rocks brought home by US astronauts.

The findings make for a clearer picture of our cosmic neighbour, once viewed as an arid expanse, but now considered a frost-coated rock that holds water throughout.

The latest results come from studies on the most extraordinary samples hauled back from the moon, including green-tinged stone collected by Apollo 15 in 1971, and orange material gathered by Apollo 17 in 1972.

The surprise discovery of the green rock, by Commander Dave Scott and lunar module pilot Jim Irwin, sparked a lengthy debate among the astronauts about the boulder's true colour while Nasa controllers listened in.

Scientists focused on tiny droplets of volcanic glass that were trapped in crystals inside the rocks. The crystals protected the droplets from the violence of eruption, and so preserved in them a snapshot of the moon's ancient interior.

Researchers found evidence for water inside the glass droplets in earlier work but the latest study goes further, showing that the lunar water is chemically identical to that on ancient Earth.

Much of Earth's water is thought to have arrived in meteorites called carbonaceous chondrites that ploughed into the planet as it formed in the early solar system.

According to the leading theory, the moon was created some time later, about 4.5bn years ago, from a hot cloud of debris that was knocked into space when a planet the size of Mars slammed into Earth.

The latest findings suggest the Earth was already damp at the time the moon was created, and that the intense heat of the collision failed to vapourise all of the water. "Some of that water survived the impact, and that's what we see in the moon," said Alberto Saal, a geologist at Brown University.

Scientists can tell roughly where in the solar system water came from by analysing its chemical signature. Water that formed far from the sun contains proportionally more deuterium, a heavy isotope of hydrogen, than water that formed closer to the sun.

When Saal's team studied water in the glass droplets, they found the ratio of deuterium to normal hydrogen was fairly low, and matched that of water found in carbonaceous chondrites. As much as 98% of Earth's water may have come from these primitive meteorites.

"The water in the moon came from the same source that brought the water to Earth, and that was carbonaceous chondrites," Saal told the Guardian.

Carbonaceous chondrites formed in the asteroid belt near Jupiter and are among the oldest objects in the solar system. The findings, reported in the journal Science, rule out comets as the source of the moon's water. Comets form in the farthest reaches of the solar system, and water inside them tends to have a higher ratio of deuterium to hydrogen.

"The new data provide the best evidence yet that the carbon-bearing chondrites were a common source of volatiles in the Earth and the moon, and perhaps the entire inner solar system," said Erik Hauri, a co-author of the study at the Carnegie Institution of Washington.

What would be in the middle of a galaxy?

There are two things in the center of a typical galaxy.

First, there is a much higher density of stars, and gas as well. This is why the center of a galaxy tends to be brighter. This inner region of higher stellar density is called a "galactic bulge". In elliptical galaxies, which don't have spiral arm structures and instead have a more uniform appearance there is still an increase in density toward the center.

Second, most large galaxies seem to have a supermassive black hole at their center. Under the right conditions if there is a lot of matter falling into such a black hole then it can give rise to extremely energetic phenomena. Depending on the details such phenomena are given different names, such as active galactic nuclei (AGNs) or quasars or blazars (which are now understood to be subsets of AGNs). These phenomena can sometimes outshine the light from all of the other stars in the galaxy, sometimes by orders of magnitude, but they are relatively uncommon and also usually depend on a fortuitous viewing angle.

Can plants get "cancer"?

They are made out of cells and exposed to UV rays nearly all the time. So why shouldn't the UV rays ionize their cell nucleus and corrupt the DNA?

Any complex multicellular organism can be suseptible to defects in cell proliferation causing individual cells or groups of cells to develop abnormally. In animals, these defects lead to tumour formation and cancer and plants develop tumours too which can be detrimental to how they function or develop. One crucial difference between plant and animal tumours is that, unlike many animal cells, plant cells are incapable of moving as they are fixed in a cell wall matrix. As such, the 'cancer' in plants is not able to spread to other parts of the organism and rarely kills.

So why do plants develops tumours? You asked in your question whether exposure to UV light could be a cause, but as far as I can find this is not the case. A vast majority of tumours developed by plants are caused by pathogens - specialised viruses and bacteria that invade plant cells and cause defects. One of the most common plant tumours are called Crown Galls which develop in the plant stems and are caused by a specific soil bacteria. Similarly, certain fungal diseases can also lead to the development of tumour like growths.

Certain plant varieties are also suspect to spontaneous tumour formation due to genetic disorders, particularly hybrid plants. Tobacco plants, for example, are one of the most suseptible to this and hybrid can be so over-run with tumours that flower and seed development is severely comporised.

Cell found in salamanders aids cell regrowth

Researchers have identified a cell that aids limb regrowth in Salamanders. Macrophages are a type of repairing cell that devour dead cells and pathogens, and trigger other immune cells to respond to pathogens. In humans, they're also important to muscle repair, which led Dr. James Godwin, of the Australian Regenerative Medicine Institute (ARMI) at Monash University, to research whether the macrophages found inside Salamanders are related to the animal's ability to regenerate limbs. Salamanders are unique in the vertebrate world as they're capable of repairing their hearts, tails, spinal cords, brain, and regrowing limbs. This makes them an obvious candidate for regenerative research. Godwin and the team at ARMI removed the macrophages the Salamanders and found that the animals were no longer able to regenerate limbs. He believes that the cells release chemicals that are vital to the Salamanders' regenerative powers. More research is needed to establish exactly how regeneration works, and Godwin is currently conducting experiments to investigate. "This really gives us somewhere to look for what might be secreted into the wound environment that allows for regeneration," he tells ABC News.

Although understanding the Salamander's abilities may one day lead to impossible-sounding feats like limb regeneration in humans, there are more-immediate benefits that could come from the research. Less ambitious goals such as scarless healing, could be attainable. "The long-term plan is that we'll know exactly what cocktail to add to a wound site to allow salamander-like regeneration under hospital conditions."

Alligator stem cells could offer tooth regeneration in humans

Humans naturally only have two sets of teeth – baby teeth and adult teeth. Ultimately, we want to identify stem cells that can be used as a resource to stimulate tooth renewal in adult humans who have lost teeth. But, to do that, we must first understand how they renew in other animals and why they stop in people,” Prof Chuong said.

Whereas most vertebrates can replace teeth throughout their lives, human teeth are naturally replaced only once, despite the lingering presence of a band of epithelial tissue called the dental lamina, which is crucial to tooth development.

Because alligators have well-organized teeth with similar form and structure as mammalian teeth and are capable of lifelong tooth renewal, the team reasoned that they might serve as models for mammalian tooth replacement.

“Alligator teeth are implanted in sockets of the dental bone, like human teeth. They have 80 teeth, each of which can be replaced up to 50 times over their lifetime, making them the ideal model for comparison to human teeth,” explained study lead author Prof Ping Wu, also from the University of Southern California.

The team found that each alligator tooth is a complex unit of three components – a functional tooth, a replacement tooth, and the dental lamina – in different developmental stages. The tooth units are structured to enable a smooth transition from dislodgement of the functional, mature tooth to replacement with the new tooth. Identifying three developmental phases for each tooth unit, the researchers conclude that the alligator dental laminae contain what appear to be stem cells from which new replacement teeth develop.

“Stem cells divide more slowly than other cells,” said co-author Prof Randall Widelitz of the University of Southern California.

“The cells in the alligator’s dental lamina behaved like we would expect stem cells to behave. In the future, we hope to isolate those cells from the dental lamina to see whether we can use them to regenerate teeth in the lab.”

The team also intends to learn what molecular networks are involved in repetitive renewal and hope to apply the principles to regenerative medicine in the future.