In various settings, including chemical reactions in the lab, inside nuclear reactors, and in outer space, scientists have found C2– anions living for as long as three milliseconds before decaying to a more stable state — and they haven’t been able to explain why. Normally particles, atoms, and molecules make these transitions to lose energy and become more stable. And normally the C2– molecule has around 4 eV less energy than the C2– anion, so the latter decayed to the former within one-trillionth of a second. The puzzle was that scientists didn’t know of a mechanism that allowed C2– to not decay to C2 for more than 3 ms, a timespan more than a billion-times longer.
In two new papers published on October 31 (here and here), researchers from Austria, the Czech Republic, and Germany reported “strong evidence” for an idea scientists first had in the late 1990s: that the delay had something to do with rotation. Scientists have previously found rapidly rotating molecules in space — including when radiation breaks up water molecules in the interstellar medium and in the dynamic neighbourhood of a newborn star.
The study team found that when the C2– complex rotates fast enough to increase its rotation quantum number 𝑁 beyond 155, it acquires a “centrifugal potential” that rearranges the lower-energy states to which C2– can decay. In particular, the team’s theoretical calculations revealed that a different state other than the C2 state to which it normally decays has lower energy, and dropping to the C2 state becomes unfavourable. More specifically, if the C2– anion had 𝑁 values in the 165-183 range, the normal decay to C2 requires electrons to have at least six units of angular momentum. If 𝑁 is lower than 165, the rearrangement of energy states doesn’t forbid the rapid drop to C2.
In other words, the spinning molecule spits out a spinning electron to move to a more stable configuration — and even then not before living to the ripe old age of 3 ms. This so-called rotation-assisted stability of the C2– anion isn’t entirely new. Other scientists have previously found dihydrogen and dideuterium anions (H2– and D2–) to be more stable as well when 𝑁 = 20-40. Using and theory and experiments, the European team found C2– acquired the same stability gain at 𝑁 of 155 or more because it’s heavier and has a higher rotational constant (“a fundamental parameter describing the rotational energy levels of a molecule,” per Meta AI).
Some facts are just boring, like 1 + 1 = 2. You already knew them before they were presented as such, and now that you do, it’s hard to know what to do with them. Some facts are clearly important, even if you don’t know how you can use them, like the spark plug fires after there’s fuel in the chamber. These two kinds of facts may seem far apart but you also know on some level that by repeatedly applying the first kind of fact in different combinations, to different materials in different circumstances, you get the second (and it’s fun to make this journey).
Then there are some other facts that, while seemingly simple, provoke in your mind profound realisations – not something new as much as a way to understand something deeply, so well, that it’s easy for you to believe that that single neural pathway among the multitude in your head has forever changed. It’s an epiphany.
I came across such a fact this morning when reading an article about a star that may have gone supernova. The author packs the fact into one throwaway sentence.
Roughly every second, one of the observable Universe’s stars dies in a fiery explosion.
The observable universe is 90-something billion lightyears wide. The universe was born only 13.8 billion years ago but it has been expanding since, pushed faster and faster apart by dark energy. This is a vast, vast space – too vast for the human mind to comprehend. I’m not just saying that. Scientists must regularly come up against numbers like 8E50 (8 followed by 50 zeroes), but they don’t have to be concerned about comprehending the full magnitude of those numbers. They don’t need to know how big it is in some dimension. They have the tools – formulae, laws, equations, etc. – to tame those numbers into submission, to beat them into discoveries and predictions that can be put to human use. (Then again, they do need to deal with monstrous moonshine.)
But for the rest of us, the untameability can be terrifying. How big is a number like 8E50? In kilograms, it’s about a 100-times lower than the mass of the observable universe. It’s the estimated volume of the galaxy NGC 1705 in cubic metres. It’s approximately the lifespan of a black hole with the mass of the Sun. You know these facts, yet you don’t know them. They’re true but they’re also very, very big, so big that they’re well past the point of true comprehension, into the realm of the I’d-rather-not-know. Yet the sentence above affords a way to bring these numbers back.
The author writes that every second or so, a star goes supernova. According to one estimate, 0.1% of stars have enough mass to eventually become a black hole. The observable universe has 200 billion trillion stars. This means there are 2E20 stars in the universe that could become a black hole, if they’re not already. Considering the universe has lived around 38% of its life and assuming a uniform rate of black hole formation (a big assumption but should suffice to illustrate my point), the universe should be visibly darkening by now, considering photons of light shouldn’t have to travel much before encountering a black hole.
But it isn’t. The simple reason is that that’s how big the universe is. We learn about stars, other plants, black holes, nebulae, galaxies and so forth. There are lots and lots of them, sure, but you know what there is the most of? The things we often discuss the least: the interstellar medium, the space between stars, and the intergalactic medium, the space between galaxies. Places where there isn’t anything big enough, ironically, to be able to catch the popular imagination. One calculation, based on three assumptions, suggests matter occupies an incomprehensibly low fraction of the observable universe (1. 85% of this is supposed to be dark matter; 2. please don’t assume atoms are also mostly empty).
In numbers, the bigness of all this transcends comprehension – but knowing that billions upon billions of black holes still only trap a tiny amount of the light going around can be… sobering. And enlivening. Why, in the time you’ve taken to read this article, 300 more black holes will have formed. Pfft.
Early 2012. The Voyager 1 space-probe is millions of kilometres beyond the orbit of the dwarf planet Pluto. In fact, it’s in a region of space filled with scattered rocks and constantly perturbed by charged particles streaming in from outer space. Has it left the Solar System, then? Nobody is sure.
Late 2012. Scientists still aren’t sure if Voyager 1 has crossed over into the interstellar medium. The ISM is the region of the universe between stars, where the probe would definitely have been outside the Solar System. The probe’s batteries had been low for a while. An important instrument on-board that could’ve ‘sniffed’ at the charged particles and known where the probe was is dead. Only something like luck could save the day.
June 2013. Three papers published in Science discuss changes in the magnetic fields around the probe. Some measurements indicate Voyager 1 is in the ISM. Others say it’s just entered a new region of space, a ‘transition zone’ between the Solar System’s outermost fringes and the first tastes of the universe beyond.
August 2013. Luck finally struck. A storm on the surface of the Sun had ejected a massive burst of its own charged particles, way back in March 2012. They coursed in waves throughout the Solar System. When the waves met the charged particles Voyager 1 was swimming in, there was a resonating, a twang in the electromagnetic field. Some other instruments could pick that up well. It was confirmation that Voyager 1 was out and away.
September 2013. The announcement was made to much celebration.
But in December 2014, there was a surprise.
Tsunamis
When the charged particles from the Sun, called a coronal mass ejection, meet the sea of charged particles in the ISM, it’s like a big wave hitting a placid shore. There is a tsunami, a disturbance spreading outward like ripples in water. Scientists don’t know how potent these tsunamis can be, but they assumed not too much because of the distances involved as well as the timescales.
They were wrong. On December 15, NASA reported that Voyager 1 was still recording the effects of a tsunami that had been unleashed 10 months ago, in February. As Don Gurnett, professor of physics at the University of Iowa, noted, “Most people would have thought the interstellar medium would have been smooth and quiet. But these shock waves seem to be more common than we thought.”
Just like a small ball floating on the surface of a pond bobs up and down when ripples pass under it, Voyager 1’s instruments pick up a bobbing of the electromagnetic field around it. These oscillations can be translated to and relayed as a sound with rising and falling pitches. Listen to it here.
One of the telltale signs that Voyager 1 is in interstellar space is that the sea of particles – or plasma – it’s cruising through gets thicker, as if more viscous. Based on observations, the plasma density has been increasing the farther out Voyager 1 goes. “Is that because the interstellar medium is denser as Voyager moves away from the heliosphere, or is it from the shock wave itself? We don’t know yet,” said Ed Stone, project scientist for the Voyager mission at Caltech.
If you’ve listened to the audio file, you’ll see how eerie it feels. The Sun’s coronal mass ejection behaves like a lighthouse in this sense. As its light – in the form of the charged particles – sweeps through space, the little boat called Voyager 1 finds its way in a rough and uncharted sea, one bob at a time. Here’s to the Sun keeping it going.
A TEXUS mission sounding rocket taking off in March 2011 from Kiruna, Sweden. Image: Adrian Mettauer
A team of European scientists have shown that DNA molecules can withstand the rough temperatures and pressures that rockets experience when they reenter Earth’s atmosphere from space. Their finding is important from the perspective of meteorites and other space rocks that crash on Earth. Many scientists think such objects could once have seeded our planet with the first molecules of life, billions of years ago.
The scientists had attached bits of plasmid DNA – the part physically separated from chromosomal DNA in biological cells and capable of reproducing independently – on 15 different parts of the outer shell of a TEXUS mission sounding rocket (powered by the Brazilian VSB-30 motor). On March 29, 2011, the rocket took off from the European Space and Sounding Rocket Range near Kiruna, Sweden, for a suborbital flight that exposed the DNA to the vacuum and low temperatures of space before shooting back toward Earth, exposing the samples to friction against the atmosphere.
The entire flight lasted 780 seconds and reached a height of 268 km. While going up, the acceleration maxed at 13.5 g and while coming down, 17.6 g. When outside Earth’s atmosphere, the rocket and samples also experienced about 378 seconds of microgravity. The maximum temperature experienced during atmospheric reentry was just below 130 degrees Celsius on the surface of the rocket; the gases in the air around the samples attached to the sides of the rocket could have reached 1,000 degrees Celsius.
A schematic showing the design of the TEXUS-49 payload and the various positions at which the DNA samples were attached. For full caption, see footnote. Image: Screenshot from paper
Promising results
In all, a maximum of 53% of the DNA could be recovered intact and 35% was fully biologically functional. Analysis also showed that “DNA applied to the bottom side of the payload had the highest degree of integrity followed by the samples applied in the grooves of the screw heads”, according to the study paper. It was published in PLOS ONE on November 26.
The ability of the DNA molecules to sustain life was then recorded by observing how many bacterial colonies each of the 15 samples could engender per nanogram. The 100% transformation efficiency was set at 1,955 colonies/nanogram, which was what an unaffected bit of plasmid DNA could achieve.
Curiously, for sample #1, which was attached on the side of the rocket where there was minimum shielding especially during atmospheric reentry, 69 colonies/nanogram were identified. The highest density of colonies was for sample #10, which was attached in the grooves of screw-heads on the rocket: 1,368/nanogram.
“We were totally surprised,” said Cora Thiel and Oliver Ullrich, coauthors of the study and biologists at the University of Zurich, in a statement. “Originally, we designed this experiment as a technology test for biomarker stability during spaceflight and reentry. We never expected to recover so many intact and functional active DNA.”
Last molecule standing
It’s clear that the damage inflicted on the DNA samples by the harsh conditions of acceleration, microgravity, temperature fluctuations, solar radiation and cosmic rays may not have been sufficient in deterring the molecules from retaining their biological functions. In fact, this study imposes new lower limits on the survivability of life: it may not be as fragile as we like to think it is.
Scientists have known temperature to be the most effective destroyer of DNA double-strands. Studies in the past have shown that the molecules weren’t able to withstand more than 95 degrees Celsius for more than five minutes without becoming denatured. During the TEXUS-49 mission, bacterial plasmid DNA temporarily withstood up to 130 degrees Celsius, maybe more.
By extension, it is not inconceivable that a fragment of a comet could have afforded any organic molecules on-board the same kind of physical shielding that a TEXUS-49 sounding rocket did. Studies dating from the mid-1970s have also shown that adding magnesium chloride or potassium chloride to the DNA further enhances its ability to withstand high temperatures without breaking down.
How big a hurdle is that out of the way? Pretty big. If DNA can put itself through as much torture and live to tell the tale, there’s no need for it to have been confined to Earth, trapped under the blanket of its atmosphere. In fact, in 2013, scientists from the Indian Center for Space Physics were able to show, through computer simulations, that biomolecules like DNA bases and amino acids are capable of being cooked up in the interstellar medium – the space between stars – where they could latch on to trespassing comets or asteroids and bring themselves into the Solar System.
According to the study, published in New Astronomy in April 2013, cosmic rays from stars can heat up particles in the interstellar medium and promote the formation of so-called precursor molecules – such as methyl isocyanate, cyanamide and cyanocarbene – which then go on to form amino acids. The only conditions his team presupposed were a particle density of 10,000-100,000 per cubic centimeter and an ambient temperature of 10 kelvin to say about 1 gram of amino acids could be present in 1014 kg of matter.
Compared to the mass density of the observable universe (9.9 × 10-27 kg/m3), that predicted density of amino acids, if true, is quite high. So, the question arises: Could we be aliens?
The first experiments
The first studies to entertain this possibility and send hapless living things to space and back began as far back as 1966, in the early days of the Space Age, alongside the Gemini IX and XII missions. Prominent missions since then include the Spacelab 1 launch (1983), the Foton 9, 11 and 12 rockets (1994-1999), the Foton M2 and M3 missions (2005-2007) and ISS EXPOSE-R mission (2009-2011). The Foton launches hosted the STONE and BIOPAN missions, which investigated if microbial lifeforms such as bacteria and fungi could survive conditions in space, such as a low temperature, solar radiation and microgravity.
Through most of these missions, scientists were able to find that the damage to lifeforms often extended down to the DNA-level. Now, we’re one step closer to understanding exactly what kind of damage is inflicted, and if there are simple ways for them to be fended off like with the addition of salts.
The STONE-5 mission (2005) was particularly interesting because it also tested how rocks would behave during atmospheric reentry, being a proxy for meteorites. It was found that the surface of a rock reached temperatures of more than 1,800 degrees Celsius. However, mission scientists concluded that if the rock layer had been thick enough (at least more than 5 mm as during the test, or 2 cm during STONE-6) to provide insulation, the innards could survive.
Fragment of the Murchison meteorite (at right) and isolated individual particles (shown in the test tube). Image: Wikimedia Commons
In the same vein, the ultimate experiments – though not performed by humans – could have been the Murchison meteorite that crashed near a town of the same name in Australia in 1969 and the Black Beauty, a rock of Martian origins, that splintered over the Sahara a thousand years ago. The Murchison meteorite was found to contain more than 70 different amino acids, only 19 of which are found on Earth. The Black Beauty was found to be 4.4 billion years old and made of sediments, signalling that a young Mars did have water.
Their arrivals’ prime contribution to humankind was that they turned our eyes skyward in the search of our origins. The experiments conducted with the TEXUS-49 mission keep them there.
Full caption for second image: a Scheme of the TEXUS 49 payload with DNA sample 1–12 application sites b Plasmid DNA samples 1–12 were applied on the outside of the TEM (TEXUS Experiment Module) EML 4 cI DNA samples 1–4 were applied circular at 0, 90, 180, 270 degree directly on the surface of the payload DNA samples 5–12 were also applied with a distance of 90 degree each in the screw heads of the payload c II DNA samples 13–15 were applied directly on the payload surface at the bottom side d DNA samples 1–4 were pipetted directly on the surface and locations were marked with a pen e DNA samples 5–12 were applied in the grooves of the screw heads f DNA samples 13–15 were applied directly on the payload surface on the bottom side and locations were marked with a pen.
A NASA photograph of the Voyager space probe, 1977. Photo: Wikimedia Commons
On September 5, 1977, NASA launched the Voyager 1 space probe to study the Jovian planets Jupiter and Saturn, and their moons, and the interstellar medium, the gigantic chasm between various star-systems in the universe. It’s been 35 years and 9 months, and Voyager has kept on, recently entering the boundary between our System and the Milky Way.
In 2012, however, when nine times farther from the Sun than is Neptune, the probe entered into a part of space completely unknown to astronomers.
On June 27, three papers were published in Science discussing what Voyager 1 had encountered, a region at the outermost edge of the Solar System they’re calling the ‘heliosheath depletion region’. They think it’s a feature of the heliosphere, the imagined bubble in space beyond whose borders the Sun has no influence.
“The principal result of the magnetic field observations made by our instrument on Voyager is that the heliosheath depletion region is a previously undetected part of the heliosphere,” said Dr. Leonard Burlaga, an astrophysicist at the NASA-Goddard Space Flight Centre, Maryland, and an author of one of the papers.
“If it were the region beyond the heliosphere, the interstellar medium, we would have expected a change in the magnetic field direction when we crossed the boundary of the region. No change was observed.”
More analysis of the magnetic field observations showed that the heliosheath depletion region has a weak magnetic field – of 0.1 nano-Tesla (nT), 0.6 million times weaker than Earth’s – oriented in such a direction that it could only have arisen because of the Sun. Even so, this weak field was twice as strong as what lay outside it in its vicinity. Astronomers would’ve known why, Burlaga clarifies, if it weren’t for the necessary instrument on the probe being long out of function.
When the probe crossed over into the region, this spike in strength was recorded within a day. Moreover, Burlaga and others have found that the spike happened thrice and a drop in strength twice, leaving Voyager 1 within the region at the time of their analysis. In fact, after August 25, 2012, no drops have been recorded. The implication is that it is not a smooth region.
“It is possible that the depletion region has a filamentary character, and we entered three different filaments. However, it is more likely that the boundary of the depletion region was moving toward and away from the sun,” Burlaga said.
The magnetic field and its movement through space are not the only oddities characterising the heliosheath depletion region. Low-energy ions blown outward by the Sun constantly emerge out of the heliosphere, but they were markedly absent within the depletion region. Burlaga was plainly surprised: “It was not predicted or even suggested.”
Analysis by Dr. Stamatios Krimigis, the NASA principal investigator for the Low-Energy Charged Particle (LECP) experiment aboard Voyager 1 and an author of the second paper, also found that cosmic rays, which are highly energised charged particles produced by various sources outside the System through unknown mechanisms, weren’t striking Voyager’s detectors equally from all directions. Instead, more hits were being recorded in certain directions inside the heliosheath depletion region.
Burlaga commented, “The sharp increase in the cosmic rays indicate that cosmic rays were able to enter the heliosphere more readily along the magnetic fields of the depletion region.”
Even though Voyager 1 was out there, Krimigis feels that humankind is blind: astronomers’ models were, are, clearly inadequate, and there is no roadmap of what lies ahead. “I feel like Columbus who thought he had gotten to West India, when in fact he had gone to America,” Krimigis contemplates. “We find that nature is much more imaginative than we are.”
With no idea of how the strange region originated or whence, we’ll just have to wait and see what additional measurements tell us. Until then, the probe will continue approaching the gateway to the Galaxy.
(This blog post first appeared on The Copernican on June 28, 2013.)
