Archive for ‘Astronomy’

November 4, 2011

Life on Mars Driven Underground?

According to Andrew Marvell, “The grave’s a fine and private place, But none I think do there embrace.”

It’s also a lonely place – and so, as far as we can now tell, the grave and the universe have a lot in common. This is probably why humans have such a desperate need to imagine life existing elsewhere in the universe.

Well, planetary scientists are on the same page, and they keep coming up with evidence that life might, just possibly, have existed on Mars at some time, probably in the distant past. Even if it’s only bacteria. Hey, that may be better than nothing, though bacteria aren’t normally considered especially huggable.

Not too long ago, it came out that at one time – oh, about 4 billion years ago – there may have been somewhere on Mars that was almost Earthlike balmy, and wet as well.

But the very latest research suggests that somewhere was subterranean. (Yes, it’s not quite the applicable term on Mars.)

Life on Mars Driven Underground?

Today’s cold, dry, and likely lifeless martian surface extends back in martian history past the time when life was taking hold on Earth, according to a new study. But researchers have also found that liquid and likely warm water persisted kilometers below the surface at the same critical time for life. Not exactly Darwin’s “warm little pond” for the beginnings of biology, but it might well have served.

It might have served, if the life there didn’t tend to be claustrophobic.

NASA Study: On Mars, Water Went Underground

Discovery of clay minerals on Mars in 2005 indicated the planet once hosted warm, wet conditions. If those conditions existed on the surface for a long era, the planet would have needed a much thicker atmosphere than it has now, to keep the water from evaporating or freezing. Researchers have sought evidence of processes by which such a thick atmosphere may have been lost over time.

This new study supports an alternative hypothesis, that persistent warm water was confined to the subsurface and that many erosional features were carved during brief periods when liquid water was stable at the surface.

That’s not a deal-breaker for the existence of (bacterial) life, since there’s substantial evidence that Earth has a thriving biosphere deep beneath the surface. But still, that seems a lot more like a crypt than a Cozumel.

Further reading:

NASA Study of Clays Suggests Watery Mars Underground

Mars’ history is a fluid situation

Subsurface water and clay mineral formation during the early history of Mars

October 14, 2011

Researchers Take the Temperature of Mars’ Past

Suppose you were told that it was possible to determine the surface temperature and presence of water on some planet other than Earth – at at time more than 4 billion years in the past? Sounds a little far-fetched, no? In fact, the deduction actually seems quite plausible, if you consider the reasoning.

The specific finding is that about 4 billion years ago, there was a spot on Mars that was wet and enjoying essentially shirt-sleeve weather – actually a bit warmer than a typical summer day on the beach at San Francisco.

How could anyone figure that out? Well, in the first place, a piece of Mars landed on Earth about 13,000 years ago in the form of a meteorite known as ALH84001. Standard methods of isotopic analysis established that minerals in the rock crystallized about 4 billion years ago.

But that’s only the beginning of the story. Carbonates in the minerals (which must have formed somewhat before the minerals themselves crystallized) contained rare isotopes of carbon and oxygen (carbon-13 and oxygen-18). The exact ratio of these two isotopes depends on the temperature at which the carbonates originally formed. That temperature must have been around 18° C. And the only way that carbonates could have formed at that temperature was by precipitation from liquid water. Voilà.

If this conclusion holds up, it will be the first time that we have good evidence the surface of Mars was once considerably warmer than it is now.

Wet and Mild: Caltech Researchers Take the Temperature of Mars’s Past

Researchers at the California Institute of Technology (Caltech) have directly determined the surface temperature of early Mars for the first time, providing evidence that’s consistent with a warmer and wetter Martian past.

By analyzing carbonate minerals in a four-billion-year-old meteorite that originated near the surface of Mars, the scientists determined that the minerals formed at about 18 degrees Celsius (64 degrees Fahrenheit). “The thing that’s really cool is that 18 degrees is not particularly cold nor particularly hot,” says Woody Fischer, assistant professor of geobiology and coauthor of the paper.

October 9, 2011

Science begins at world’s most complex ground-based astronomy observatory

The electromagnetic spectrum comprises “radiation” of many types whose fundamental similarity is usually overlooked – from radio at the low-energy end to gamma rays at the high end. Whether one measures it in frequency, wavelength, or photon energy, the difference from one end to the other is more than 15 orders of magnitude. In principle, there is neither an upper nor lower limit, though the extremes are uncommon in nature.

All forms of EM radiation result fundamentally from the oscillations of electrical charges. All forms carry information encoded in these oscillations. Radio waves have lengths typically measured in meters. They were the first type of EM radiation used for communication, because the atmosphere is transparent to them. The length of microwaves is measured in centimeters, and although the atmosphere is mostly transparent to microwaves, they do not easily penetrate solid objects. There’s an atmospheric window for visible light and infrared radiation, with wavelengths measured in a few hundreds of nanometers. But at shorter wavelengths (ultraviolet, ~400 nm) the atmosphere again becomes opaque – fortunately for living things.

Astronomy can, in principle, be done at any wavelength, from radio to gamma rays, and there is astronomically interesting information at all wavelengths. In cases where the atmosphere is transparent to the radiation, astronomy can be done from the ground (though higher elevations are better, to be above dust, water vapor, and clouds). Otherwise it must be done from space.

One especially interesting case is the millimeter and sub-millimeter wavelength band, lying between microwaves and far infrared. Very little astronomical work has been done in this band, because the atmosphere is mostly opaque to those wavelengths, and because it has been technically difficult to build receivers for this range.

However, by using the latest technology and locating facilities at high elevations above most of the atmosphere, astronomers are about to gain access to this range for the first time.

ALMA Opens Its Eyes

Humanity’s most complex ground-based astronomy observatory, the Atacama Large Millimeter/submillimeter Array (ALMA), has officially opened for astronomers. The first released image, from a telescope still under construction, reveals a view of the Universe that cannot be seen at all by visible-light and infrared telescopes. Thousands of scientists from around the world have competed to be among the first few researchers to explore some of the darkest, coldest, furthest, and most hidden secrets of the cosmos with this new astronomical tool.

At present, around a third of ALMA’s eventual 66 radio antennas, with separations up to only 125 metres rather than the maximum 16 kilometres, make up the growing array on the Chajnantor plateau in northern Chile, at an elevation of 5000 metres. And yet, even under construction, ALMA has become the best telescope of its kind — as reflected by the extraordinary number of astronomers who requested time to observe with ALMA.

What types of astronomical questions can be investigated in this newly opened territory?


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