Wednesday Reader: NASA Finds Nitrogen on Mars; Astronomy’s “Big Crunch”

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The good news: there is nitrogen on Mars.

The bad news: the universe will collapse on itself, according to a new study.

First, the good news…

This (really gigantic) self-portrait of NASA's Mars rover Curiosity combines dozens of exposures taken by the rover's Mars Hand Lens Imager on Feb. 3, 2013 plus three exposures taken May 10, 2013 to show two holes (in lower left quadrant) where Curiosity used its drill on the rock target "John Klein". Image Credit: NASA/JPL-Caltech/MSSS

This (really gigantic) self-portrait of NASA’s Mars rover Curiosity combines dozens of exposures taken by the rover’s Mars Hand Lens Imager on Feb. 3, 2013 plus three exposures taken May 10, 2013 to show two holes (in lower left quadrant) where Curiosity used its drill on the rock target “John Klein”.
Image Credit: NASA/JPL-Caltech/MSSS

NASA’s Curiosity Rover Finds Biologically Useful Nitrogen on Mars

A team using the Sample Analysis at Mars (SAM) instrument suite aboard NASA’s Curiosity rover has made the first detection of nitrogen on the surface of Mars from release during heating of Martian sediments. The nitrogen was detected in the form of nitric oxide, and could be released from the breakdown of nitrates during heating. Nitrates are a class of molecules that contain nitrogen in a form that can be used by living organisms. The discovery adds to the evidence that ancient Mars was habitable for life.

Nitrogen is essential for all known forms of life, since it is used in the building blocks of larger molecules like DNA and RNA, which encode the genetic instructions for life, and proteins, which are used to build structures like hair and nails, and to speed up or regulate chemical reactions.

However, on Earth and Mars, atmospheric nitrogen is locked up as nitrogen gas (N2) – two atoms of nitrogen bound together so strongly that they do not react easily with other molecules. The nitrogen atoms have to be separated or “fixed” so they can participate in the chemical reactions needed for life. On Earth, certain organisms are capable of fixing atmospheric nitrogen and this process is critical for metabolic activity. However, smaller amounts of nitrogen are also fixed by energetic events like lightning strikes.

Nitrate (NO3) – a nitrogen atom bound to three oxygen atoms – is a source of fixed nitrogen. A nitrate molecule can join with various other atoms and molecules; this class of molecules is known as nitrates.

There is no evidence to suggest that the fixed nitrogen molecules found by the team were created by life. The surface of Mars is inhospitable for known forms of life. Instead, the team thinks the nitrates are ancient, and likely came from non-biological processes like meteorite impacts and lightning in Mars’ distant past.

Features resembling dry riverbeds and the discovery of minerals that only form in the presence of liquid water suggest that Mars was more hospitable in the remote past. The Curiosity team has found evidence that other ingredients needed for life, such as liquid water and organic matter, were present on Mars at the Curiosity site in Gale Crater billions of years ago.

“Finding a biochemically accessible form of nitrogen is more support for the ancient Martian environment at Gale Crater being habitable,” said Jennifer Stern of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Stern is lead author of a paper on this research published online in the Proceedings of the National Academy of Science March 23.

The team found evidence for nitrates in scooped samples of windblown sand and dust at the “Rocknest” site, and in samples drilled from mudstone at the “John Klein” and “Cumberland” drill sites in Yellowknife Bay. Since the Rocknest sample is a combination of dust blown in from distant regions on Mars and more locally sourced materials, the nitrates are likely to be widespread across Mars, according to Stern. The results support the equivalent of up to 1,100 parts per million nitrates in the Martian soil from the drill sites. The team thinks the mudstone at Yellowknife Bay formed from sediment deposited at the bottom of a lake. Previously the rover team described the evidence for an ancient, habitable environment there: fresh water, key chemical elements required by life, such as carbon, and potential energy sources to drive metabolism in simple organisms.

The samples were first heated to release molecules bound to the Martian soil, then portions of the gases released were diverted to the SAM instruments for analysis. Various nitrogen-bearing compounds were identified with two instruments: a mass spectrometer, which uses electric fields to identify molecules by their signature masses, and a gas chromatograph, which separates molecules based on the time they take to travel through a small glass capillary tube — certain molecules interact with the sides of the tube more readily and thus travel more slowly.

Along with other nitrogen compounds, the instruments detected nitric oxide (NO — one atom of nitrogen bound to an oxygen atom) in samples from all three sites. Since nitrate is a nitrogen atom bound to three oxygen atoms, the team thinks most of the NO likely came from nitrate which decomposed as the samples were heated for analysis. Certain compounds in the SAM instrument can also release nitrogen as samples are heated; however, the amount of NO found is more than twice what could be produced by SAM in the most extreme and unrealistic scenario, according to Stern. This leads the team to think that nitrates really are present on Mars, and the abundance estimates reported have been adjusted to reflect this potential additional source.

“Scientists have long thought that nitrates would be produced on Mars from the energy released in meteorite impacts, and the amounts we found agree well with estimates from this process,” said Stern.

The SAM instrument suite was built at NASA Goddard with significant elements provided by industry, university, and national and international NASA partners. NASA’s Mars Science Laboratory Project is using Curiosity to assess ancient habitable environments and major changes in Martian environmental conditions. NASA’s Jet Propulsion Laboratory in Pasadena, California, a division of Caltech, built the rover and manages the project for NASA’s Science Mission Directorate in Washington. The NASA Mars Exploration Program and Goddard Space Flight Center provided support for the development and operation of SAM. SAM-Gas Chromatograph was supported by funds from the French Space Agency (CNES). Data from these SAM experiments are archived in the Planetary Data System (pds.nasa.gov).

Okay, now the not-so-good news…

This is the "South Pillar" region of the star-forming region called the Carina Nebula. Like cracking open a watermelon and finding its seeds, the infrared telescope "busted open" this murky cloud to reveal star embryos tucked inside finger-like pillars of thick dust. Credit: NASA NASA's Spitzer Space Telescope has captured a new, infrared view of the choppy star-making cloud called M17, also known as the Omega Nebula or the Swan Nebula.  The cloud, located about 6,000 light-years away in the constellation Sagittarius, is dominated by a central group of massive stars -- the most massive stars in the region. These central stars give off intense flows of expanding gas, which rush like rivers against dense piles of material, carving out the deep pocket at center of the picture. Winds from the region's other massive stars push back against these oncoming rivers, creating bow shocks like those that pile up in front of speeding boats. Three of these bow shocks are nestled in the upper left side of the central cavity, but are difficult to spot in this view. They are composed of compressed gas in addition to dust that glows at infrared wavelengths Spitzer can see. The smiley-shaped bow shocks curve away from the stellar winds of the central massive stars. This picture was taken with Spitzer's infrared array camera. It is a four-color composite, in which light with a wavelength of 3.6 microns is blue; 4.5-micron light is green; 5.8-micron light is orange; and 8-micron light is red. Dust is red, hot gas is green and white is where gas and dust intermingle. Foreground and background stars appear scattered through the image.

This is the “South Pillar” region of the star-forming region called the Carina Nebula. Like cracking open a watermelon and finding its seeds, the infrared telescope “busted open” this murky cloud to reveal star embryos tucked inside finger-like pillars of thick dust. Credit: NASA
NASA’s Spitzer Space Telescope has captured a new, infrared view of the choppy star-making cloud called M17, also known as the Omega Nebula or the Swan Nebula.
The cloud, located about 6,000 light-years away in the constellation Sagittarius, is dominated by a central group of massive stars — the most massive stars in the region. These central stars give off intense flows of expanding gas, which rush like rivers against dense piles of material, carving out the deep pocket at center of the picture. Winds from the region’s other massive stars push back against these oncoming rivers, creating bow shocks like those that pile up in front of speeding boats.
Three of these bow shocks are nestled in the upper left side of the central cavity, but are difficult to spot in this view. They are composed of compressed gas in addition to dust that glows at infrared wavelengths Spitzer can see. The smiley-shaped bow shocks curve away from the stellar winds of the central massive stars.
This picture was taken with Spitzer’s infrared array camera. It is a four-color composite, in which light with a wavelength of 3.6 microns is blue; 4.5-micron light is green; 5.8-micron light is orange; and 8-micron light is red. Dust is red, hot gas is green and white is where gas and dust intermingle. Foreground and background stars appear scattered through the image.

The Universe may be on the brink of collapse (but don’t worry – you have about 10 billion years to make other plans)

Physicists have proposed a mechanism for “cosmological collapse” that predicts that the universe will soon stop expanding and collapse in on itself, obliterating all matter as we know it. Their calculations suggest that the collapse is “imminent”—on the order of a few tens of billions of years or so—which may not keep most people up at night, but for the physicists it’s still much too soon.

In a paper published in Physical Review Letters, physicists Nemanja Kaloper at the University of California, Davis; and Antonio Padilla at the University of Nottingham have proposed the cosmological collapse mechanism and analyzed its implications, which include an explanation of dark energy.

“The fact that we are seeing dark energy now could be taken as an indication of impending doom, and we are trying to look at the data to put some figures on the end date,” Padilla said in an email. “Early indications suggest the collapse will kick in in a few tens of billions of years, but we have yet to properly verify this.”

The main point of the paper is not so much when exactly the universe will end, but that the mechanism may help resolve some of the unanswered questions in physics. In particular, why is the universe expanding at an accelerating rate, and what is the dark energy causing this acceleration? These questions are related to the cosmological constant problem, which is that the predicted vacuum energy density of the universe causing the expansion is much larger than what is observed.

“I think we have opened up a brand new approach to what some have described as ‘the mother of all physics problems,’ namely the cosmological constant problem,” Padilla said. “It’s way too early to say if it will stand the test of time, but so far it has stood up to scrutiny, and it does seem to address the issue of vacuum energy contributions from the standard model, and how they gravitate.”

The collapse mechanism builds on the physicists’ previous research on vacuum energy sequestering, which they proposed to address the cosmological constant problem. The dynamics of vacuum energy sequestering predict that the universe will collapse, but don’t provide a specific mechanism for how collapse will occur.

According to the new mechanism, the universe originated under a set of specific initial conditions so that it naturally evolved to its present state of acceleration and will continue on a path toward collapse. In this scenario, once the collapse trigger begins to dominate, it does so in a period of “slow roll” that brings about the accelerated expansion we see today. Eventually the universe will stop expanding and reach a turnaround point at which it begins to shrink, culminating in a “big crunch.”

Currently, we are in the period of accelerated expansion, and we know that the universe is approximately 13.8 billion years old. So in order for the new mechanism to work, the period of accelerated expansion must last until at least this time (needless to say, a mechanism that predicts that the universe has already collapsed is obviously flawed). The collapse time can be delayed by choosing an appropriate slope, which in this case, is a slope that has a very tiny positive value—about 10-39 in the scientists’ equation. The very gradual slope means that the universe evolves very slowly.

Importantly, the scientists did not choose a slope just to fit the observed expansion and support their mechanism. Instead, they explain that the slope is “technically natural,” and takes on this value due to a symmetry in the theory.

As the physicists explain, the naturalness of the mechanism makes it one of the first ever models that predicts acceleration without any direct fine-tuning. In the mechanism, the slope alone controls the universe’s evolution, including the scale of the accelerated expansion.

“The ‘technically natural’ size of the slope controls when the collapse trigger begins to dominate, but was it guaranteed to give us slow roll and therefore the accelerated expansion?” Padilla said. “Naively one might have expected to have to fine-tune some initial conditions to guarantee this, but remarkably that is not the case. The dynamics of vacuum energy sequestering guarantee the slow roll.”

The idea is still in its early stages, and the physicists hope to build on it much more in the future.

“There is much to do,” Padilla said. “Right now we are working on a way to describe our theory in a way that is manifestly local, which will make it more conventional, and more obviously in keeping with some of the key principles behind quantum theory (namely, linear superposition). We would also like to devise more tests of the idea, both cosmological and astrophysical.

“Over the longer term, we would like to understand how our theory could emerge from a more fundamental theory, such as string theory. It is also important to ask what happens when we consider vacuum energy corrections from quantum gravity.”

If there was ever a justification that more work is needed, it may be in the paper’s conclusion:

“The present epoch of acceleration may be evidence of impending doom. . . A detailed analysis to better quantify these predictions is certainly warranted.”

As I said, you have plenty of time to make other plans.

Pack well.

Crash

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