Wednesday, August 29, 2012

The dangers of nanoparticles: Even plants are affected by tiny nanoparticles as they disrupt the physiological functions

Metal Nanoparticles Hurt Soybean Growth

Soybeans are the second largest crop harvested in the United States and a $30-billion-a-year industry. But soybean production could face a new long-term threat from large amounts of metallic nanoparticles in the environment, says a report in the journal Science.
A new study reveals that one type of these nano-sized materials, found in everything from cosmetics to electronic devices, can be absorbed by soybeans and move throughout their tissues, while another type of nanoparticle likely stunts their growth. The findings, the authors say, raise concerns about the impact of nanoparticles on a host of other crops.
Metal contamination has long been a concern in agriculture. The U.S. Environmental Protection Agency currently requires companies that discharge potentially toxic metals into wastewater to remove the metals before the water is sent to wastewater treatment plants. Half of the organic material collected from such treatment plants eventually ends up on farmers' fields as fertilizer. However, the presence of metal nanoparticles in wastewater is neither regulated nor monitored. And, within a decade, industry could be producing millions of metric tons of some metal nanoparticles per year, raising concerns about their accumulation in the environment.
Such concerns have already prompted some initial studies looking for possible biological impacts. In 2010, researchers led by Jorge Gardea-Torresdey, a chemist at the University of Texas, El Paso, reported inEnvironmental Science & Technology that when soybeans were grown hydroponically and exposed to high levels of zinc oxide and cerium oxide nanoparticles, those particles could accumulate in plant tissues, with cerium oxide triggering genetic damage in the plants' roots. Another study published online last month in Applied and Environmental Microbiology found that high concentrations of zinc oxide and titanium dioxide nanoparticles disrupt soil bacterial communities and interfere with the ability of rhizobia bacteria that associate with soybeans to use nitrogen from the air to produce fertilizer for the plant. This ability of soybeans to "fix" nitrogen has a major impact on agriculture. Whereas 97% of corn farmed in the United States requires fertilizer, only 18.5% of the 77 million acres of soybeans farmed in the United States each year are fertilized.
Still, it was unclear whether compounds present in the dirt would lock up nanoparticles or whether the nanoparticles would be "bioavailable," allowing plants to take them up. So for the new study, University of California, Santa Barbara, environmental microbiologist Patricia Holden, who led the Applied and Environmental Microbiology study, teamed up with Gardea-Torresdey as well as colleagues at four other institutions in the United States and South Korea to test the effect of metal nanoparticles on soybeans grown the old-fashioned way. They mixed zinc oxide and cerium oxide nanoparticles into separate batches of soil from an organic farm in California. Then they split these mixtures into several lots, each time adding a different amount of pristine soil to give the lots concentrations of metal nanoparticles that previous hydroponic studies had flagged as potentially having a biological impact. That gave them three different soil concentrations of each of the two nanoparticles. For the zinc oxide, the concentration was either 0.005, 0.1, or 0.5 grams per kilogram of soil. For cerium oxide, the concentration was either 0.1, 0.5, or 1 gram per kilogram. The team then tracked the amount of nanoparticles taken up by different tissues of the plant and the impact on their growth.
The researchers report their results online this week in the Proceedings of the National Academy of Sciences. Only plant roots and the root nodules that serve as nurseries for rhizobia absorbed cerium oxide nanoparticles. But at the mid- and high-exposure levels the plants were essentially unable to fix nitrogen. Holden says that in these cases the root nodules that normally house nitrogen-fixing bacteria were "were vacant of bacteria." But she cautions that although it appears that the cerium oxide nanoparticles are the culprit, the researchers can't yet be sure.
As for the zinc oxide, Holden's team found that these metal particles didn't seem to have any significant biological effect, though soybean tissues with high levels of the metal tended to hold less water. Still, zinc levels rose throughout the plants' tissues, even in the beans that would be used as food for humans and livestock. This high level of zinc doesn't necessarily pose a threat to people, Holden says, since the zinc levels were essentially on par with the amount of zinc recommended for people's diets in the United States. But she adds that she and her colleagues aren't sure if the zinc in soybeans is transformed into zinc ions, the form of the metal that is normally present in our bodies, or remains zinc oxide nanoparticles, which could have different biological effects.
"This is a pioneering study" that's beginning to tease out potential agricultural impacts of nanomaterials, says Andre Nel, a nanomaterials toxicologist at the University of California, Los Angeles. He is quick to add that it is unlikely that soybeans and other plants are currently exposed to nanoparticle concentrations as high as those used in the new study, but researchers aren't sure. "In the world of agricultural exposure levels, nobody knows what the nanomaterial concentration is."
"Is this an indication we should be worried about the food supply? I don't know," Holden says. The take-home message, she says, is that "there is a potential for nanomaterials to be bioavailable in soil and affect agriculture." Whether they will eventually accumulate in the high concentrations shown to have an impact here is unclear. However, she says, "it's important that the scientific community asks these questions in advance."

Tuesday, August 28, 2012

The miraculous world of ants: Do ants communicate like our Internet?

Stanford researchers discover the 'anternet'

A collaboration between a Stanford ant biologist and a computer scientist has revealed that the behavior of harvester ants as they forage for food mirrors the protocols that control traffic on the Internet.
Biologist Deborah Gordon has been studying ants for more than 20 years. (Photo: Linda A. Cicero / Stanford News Service)
On the surface, ants and the Internet don't seem to have much in common. But two Stanford researchers have discovered that a species of harvester ants determine how many foragers to send out of the nest in much the same way that Internet protocols discover how much bandwidth is available for the transfer of data. The researchers are calling it the "anternet."
Deborah Gordon, a biology professor at Stanford, has been studying ants for more than 20 years. When she figured out how the harvester ant colonies she had been observing in Arizona decided when to send out more ants to get food, she called across campus toBalaji Prabhakar, a professor of computer science at Stanford and an expert on how files are transferred on a computer network. At first he didn't see any overlap between his and Gordon's work, but inspiration would soon strike.
"The next day it occurred to me, 'Oh wait, this is almost the same as how [Internet] protocols discover how much bandwidth is available for transferring a file!'" Prabhakar said. "The algorithm the ants were using to discover how much food there is available is essentially the same as that used in the Transmission Control Protocol."
Transmission Control Protocol, or TCP, is an algorithm that manages data congestion on the Internet, and as such was integral in allowing the early web to scale up from a few dozen nodes to the billions in use today. Here's how it works: As a source, A, transfers a file to a destination, B, the file is broken into numbered packets. When B receives each packet, it sends an acknowledgment, or an ack, to A, that the packet arrived.
This feedback loop allows TCP to run congestion avoidance: If acks return at a slower rate than the data was sent out, that indicates that there is little bandwidth available, and the source throttles data transmission down accordingly. If acks return quickly, the source boosts its transmission speed. The process determines how much bandwidth is available and throttles data transmission accordingly.
It turns out that harvester ants (Pogonomyrmex barbatus) behave nearly the same way when searching for food. Gordon has found that the rate at which harvester ants – which forage for seeds as individuals – leave the nest to search for food corresponds to food availability.
A forager won't return to the nest until it finds food. If seeds are plentiful, foragers return faster, and more ants leave the nest to forage. If, however, ants begin returning empty handed, the search is slowed, and perhaps called off.
Prabhakar wrote an ant algorithm to predict foraging behavior depending on the amount of food – i.e., bandwidth – available. Gordon's experiments manipulate the rate of forager return. Working with Stanford student Katie Dektar, they found that the TCP-influenced algorithm almost exactly matched the ant behavior found in Gordon's experiments.
"Ants have discovered an algorithm that we know well, and they've been doing it for millions of years," Prabhakar said.
They also found that the ants followed two other phases of TCP. One phase is known as slow start, which describes how a source sends out a large wave of packets at the beginning of a transmission to gauge bandwidth; similarly, when the harvester ants begin foraging, they send out foragers to scope out food availability before scaling up or down the rate of outgoing foragers.
Another protocol, called time-out, occurs when a data transfer link breaks or is disrupted, and the source stops sending packets. Similarly, when foragers are prevented from returning to the nest for more than 20 minutes, no more foragers leave the nest.
Prabhakar said that had this discovery been made in the 1970s, before TCP was written, harvester ants very well could have influenced the design of the Internet.
Gordon thinks that scientists have just scratched the surface for how ant colony behavior could help us in the design of networked systems.
There are 11,000 species of ants, living in every habitat and dealing with every type of ecological problem, Gordon said. "Ants have evolved ways of doing things that we haven't thought up, but could apply in computer systems. Computationally speaking, each ant has limited capabilities, but the collective can perform complex tasks.
"So ant algorithms have to be simple, distributed and scalable – the very qualities that we need in large engineered distributed systems," she said. "I think as we start understanding more about how species of ants regulate their behavior, we'll find many more useful applications for network algorithms."
The work is published in the Aug. 23 issue of PLoS Computational Biology.

Antibiotics and body weight: An insight into this major medical and heath nexus

Do Antibiotics Make Us Fat?

Farmers have long used antibiotics to make cows, pigs, and turkeys gain weight faster. Now, scientists claim that receiving antibiotics early in life may also make children grow fat. The researchers believe the drugs change the composition of the bacterial population in the gut in a crucial developmental stage that may have a long-lasting impact.
Other scientists are casting doubt on the conclusions, however. The new data are "not convincing," says Michael Blaut, a microbiologist at the German Institute of Human Nutrition in Potsdam, Germany. And David Relman, a microbiologist at the Stanford University School of Medicine in Palo Alto, California, calls the work "provocative" but says some of the data are "a bit vague and unclear."
Billions of microbial cells live in the guts of humans and other animals. Research on these vast bacterial populations, called microbiomes, is just getting started, but scientists already know that some microbial boarders play a crucial role in breaking down nutrients in our diet. Some have also suspected that low-dose antibiotics, given to farm animals to make them grow bigger, could work by altering the gut microbiome.
To test this hypothesis, a team led by microbiologist Martin Blaser of the New York University School of Medicine in New York City added antibiotics to the drinking water of mice that had just been weaned. The medicine—either penicillin, vancomycin, a combination of the two, or chlortetracycline—was given at doses comparable to those approved by the U.S. Food and Drug Administration as growth promoters in farm animals. After 7 weeks, the group of mice on antibiotics had significantly more fat than a control group drinking plain water, the team reports online today in Nature. "This confirms what farmers have shown for 60 years, that low-dose antibiotics cause their animals to grow bigger," Blaser says.
If the findings of the study are replicated in other animal models, such as pigs, they could have considerable implications for public health, says Oluf Pedersen, professor of genomic medicine at the Novo Nordisk Foundation Center for Basic Metabolic Research at the University of Copenhagen.
Antibiotics did not reduce the overall number of microbes in the animals' guts, but it shifted their composition. DNA comparisons showed that mice treated with antibiotics had a higher proportion of bacteria belonging to the group Firmicutes than control animals. Firmicutes might be able to extract more calories from food and deliver them to the host, Blaser argues. The results are relevant to humans as well, he says. Another paper Blaser co-authored, published online in the International Journal of Obesity yesterday, reports a link between antibiotic use in infants and obesity in childhood.
The researchers looked at data collected from more than 11,000 children born in Avon, U.K., in 1991 and 1992. Those who had been treated with antibiotics in the first 6 months of their lives had a higher chance of being overweight at 10, 20, and 38 months of age. "It is an association, and that does not mean causation," says Leonardo Trasande, the paper's first author. "But coupled with the Nature paper, it begins to tell a convincing story."
Blaser argues that his work shows that antibiotic use in babies has an unappreciated cost. And while they're sometimes necessary, antibotics are often used willy-nilly, he says.
But others say caution is in order. In the human study, the differences in weight were small, and there was no correlation between antibiotic use in the first 6 months and weight at 7 years, the last time information was collected on the children. And there are many reasons why the mice experiments should not be extrapolated to humans and children, Relman says. The study was done with just one inbred line of mice. Seven weeks is a long time in mice, which mature quickly and live to be only 2 or 3 years old, he says. "We never give antibiotics to children continuously from the time they wean to the time they reach sexual maturity."
Also, the differences in fat mass between antibiotic-fed mice and controls are small, Blaut says. And Relman points out that while they became fatter, the mice's overall weight did not increase, as happens in farm animals. "Although one doesn't expect antibiotics to work the same in all species and under all circumstances, it does seem curious that there was this one effect and not the weight gain," Relman writes in an e-mail.
Finally, Relman cautions that the composition of the mouse microbiome was measured only at the end of the experiment. "This means that we don't know whether the microbiome changes were the cause of, the result of, or unrelated to the mouse fat content change," he says. Blaser calls that a valid criticism, but adds that he has begun to address this. "We have shown in further experiments that have not been published yet that transferring the microbiome also transfers the obesity from one mouse to the next."

Brain cancers and cats: Felines are safe, do not cause brain cancers in pet owners

Credit: David Grimm

A Report in Science says cats do not cause brain cancers

Last year, cat owners got a scare when a team of French researchers reported a possible link between felines and brain cancer. Cat feces can harbor a single-celled parasite called Toxoplasma gondii, and the scientists found that nations with higher rates of human T. gondii infection also have higher incidences of brain cancer. The findings were controversial, and many scientists considered the link weak. Now, another team of researchers believes it has settled the issue. The scientists examined a cohort of more than 600,000 British women aged 50 and older and tracked how many developed brain tumors over an average of 3 years. Eighteen percent of those women—more than 100,000—owned at least one cat. But the cat-owning women were no more likely to develop brain cancer than their cat-free counterparts, despite their presumably greater risk of exposure to T. gondii, the team reports online today in Biology Letters. So the next time someone scratches up your furniture, blame the cat—but when it comes to brain cancer, point the finger somewhere else. 

Unravelling the secret worlds of the Red Planet Mars

Curiosity Begins Driving at Bradbury Landing

NASA's Mars rover Curiosity has begun driving from its landing site, which scientists announced today they have named for the late author Ray Bradbury.
Making its first movement on the Martian surface, Curiosity's drive combined forward, turn and reverse segments. This placed the rover roughly 20 feet (6 meters) from the spot where it landed 16 days ago, says a NASA release.
Bradbury Landing (splash)
This panorama shows the tire tracks from Curiosity's first test drive. On Aug. 22, 2012, the rover made its first move, going forward about 15 feet (4.5 meters), rotating 120 degrees and then reversing about 8 feet (2.5 meters). Curiosity is about 20 feet (6 meters) from its landing site, now named Bradbury Landing. Image credit: NASA/JPL-Caltech 
NASA has approved the Curiosity science team's choice to name the landing ground for the influential author, who was born 92 years ago today and died this year. The location where Curiosity touched down is now called Bradbury Landing.
"This was not a difficult choice for the science team," said Michael Meyer, NASA program scientist for Curiosity. "Many of us and millions of other readers were inspired in our lives by stories Ray Bradbury wrote to dream of the possibility of life on Mars." 
Bradbury Landing (tire tracks, 200px)
A close-up view of Curiosity's first tire tracks.
Today's drive confirmed the health of Curiosity's mobility system and produced the rover's first wheel tracks on Mars, documented in images taken after the drive. During a news conference at NASA's Jet Propulsion Laboratory in Pasadena, Calif., the mission's lead rover driver, Matt Heverly, showed an animation derived from visualization software used for planning the first drive.
"We have a fully functioning mobility system with lots of amazing exploration ahead," Heverly said.
Curiosity will spend several more days of working beside Bradbury Landing, performing instrument checks and studying the surroundings, before embarking toward its first driving destination approximately 1,300 feet (400 meters) to the east-southeast.

"Curiosity is a much more complex vehicle than earlier Mars rovers. The testing and characterization activities during the initial weeks of the mission lay important groundwork for operating our precious national resource with appropriate care," said Curiosity Project Manager Pete Theisinger of JPL. "Sixteen days in, we are making excellent progress."

How to keep your bones safe in the Space through diet and exercise


Eating the right diet and exercising hard in space helps
protect International Space Station astronauts' bones, a finding that
may help solve one of the key problems facing future explorers
heading beyond low Earth orbit.

A new study, published this month in the Journal of Bone and Mineral
Research, evaluated the mineral density of specific bones as well as
the entire skeleton of astronauts who used the Advanced Resistive
Exercise Device (ARED), a 2008 addition to the space station that can
produce resistance of as much as 600 pounds in microgravity.
Resistance exercise allows astronauts to "lift weights" in

Researchers compared data measured from 2006 until the new device
arrived, when astronauts used an interim workout that offered about
half the total resistance of the ARED. The researchers found
astronauts using the advanced exercise system returned to Earth with
more lean muscle and less fat, and maintained their whole body and
regional bone mineral density compared to when they launched. Crew
members using ARED also consumed sufficient calories and vitamin D,
among other nutrients. These factors are known to support bone health
and likely played a contributing role.

"After 51 years of human spaceflight, these data mark the first
significant progress in protecting bone through diet and exercise,"
said Scott M. Smith, NASA nutritionist at the agency's Johnson Space
Center in Houston and lead author of the publication.

Since the 1990s, resistance exercise has been thought to be a key
method of protecting astronauts' bones. Normal, healthy bone
constantly breaks down and renews itself, a process called
remodeling. As long as these processes are in balance, bone mass and
density stay the same. Earlier studies of Russian Mir space station
residents found an increased rate of breakdown, but little change in
the rate of regrowth that resulted in an overall loss in bone
density. In the new study, researchers looked at preflight and
postflight images of bone using X-ray densitometry, as well as
in-flight blood and urine measurements of chemicals that reflect bone
metabolism. In crew members who used the ARED device during
spaceflight, bone breakdown still increased, but bone formation also
tended to increase, likely resulting in the maintenance of whole bone
mineral density.

"The increase in both bone breakdown and formation suggests that the
bone is being remodeled, but a key question remains as to whether
this remodeled bone is as strong as the bone before flight," said Dr.
Jean Sibonga, bone discipline lead at Johnson and coauthor of the
Studies to evaluate bone strength before and after flight are
currently under way.

Beyond bone strength, further study is required to determine the best
possible combination of exercise and diet for long-duration crews.
Dietary effects on bone are being studied on the space station right
now, with one experiment evaluating different ratios of animal
protein and potassium in the diet on bone health. Another is looking
at the benefits for bone of lowering sodium intake.

Tributes to Neil Armstrong: A brief recall of the landing of man on the lunar world

Wide Awake in the Sea of Tranquillity

Neil Armstrong was supposed to be asleep. The moonwalking was done. The moon rocks were stowed away. His ship was ready for departure. In just a few hours, the Eagle's ascent module would blast off the Moon, something no ship had ever done before, and Neil needed his wits about him. He curled up on the Eagle's engine cover and closed his eyes, says a NASA press release.
But he could not sleep.
Neither could Buzz Aldrin. In the cramped lander, Buzz had the sweet spot, the floor. He stretched out as much as he could in his spacesuit and closed his eyes. Nothing happened. On a day like this, sleep was out of the question.

Above: Apollo 11 Earthrise.
July 20, 1969: The day began on the farside of the Moon. Armstrong, Aldrin and crewmate Mike Collins flew their spaceship 60 miles above the cratered wasteland. No one on Earth can see the Moon's farside. Even today it remains a land of considerable mystery, but the astronauts had no time for sight-seeing. Collins pressed a button, activating a set of springs, and the spaceship split in two. The half named Columbia, with Collins on board, would remain in orbit. The other half, the Eagle, spiraled over the horizon toward the Sea of Tranquillity.
"You are Go for powered descent," Houston radioed, and the Eagle's engine fired mightily. The bug-shaped Eagle was so fragile a child could poke a hole through its gold foil exterior. Jagged moonrocks could do much worse. So when Armstrong saw where the computer was guiding them--into a boulder field-θΆ³he quickly took control. The Eagle pitched forward and sailed over the rocks.
Meanwhile, alarms were ringing in the background.
"Program alarm," announced Armstrong. "It's a 1202." The code was so obscure, almost no one knew what it meant. Should they abort? Should they land? "What is it?" he insisted.
Scrambling back in Houston, a young engineer named Steve Bales produced the answer: The radar guidance system was pestering the computer with too many interruptions. No problem. "We've got you..." radioed Houston. "We're Go on that alarm."

And on they went. Things, however, were not going exactly as planned. The Sea of Tranquillity was supposed to be smooth, but it didn't look so smooth from the cockpit of the Eagle. Armstrong scanned the jumbled mare for a safe place to land. "60 seconds," radioed Houston. "30 seconds." Mission control was hushed as the telemetry came in. Soon, too soon, the ship would run out of fuel.
see captionRight: Mission Control during the Apollo 11 descent.
Capcom later claimed the "boys in mission control were turning blue" when Armstrong announced "I [found] a good spot." As for Armstrong, his heart was thumping 156 beats per minute according to bio-sensors. The fuel gauge read only 5.6% when the Eagle finally settled onto the floor of the Sea of Tranquillity.
Houston (relieved): "We copy you down, Eagle."
Armstrong (coolly): "Houston, Tranquility Base here. The Eagle has landed."
Immediately, they prepared to leave. This was NASA being cautious. No one had ever landed on the Moon before. What if a footpad started sinking into the moondust, or the Eagle sprung a leak? While Neil and Buzz made ready to blast off, Houston read the telemetry looking for signs of trouble. There were none, and three hours after touchdown, finally, Houston gave the "okay." The moonwalk was on!
At 9:56 p.m. EDT, Neil descended the ladder and took "one small step" (left foot first) into history. From the shadow of the Eagle, he looked around: "It has a stark beauty all its own--like the high desert of the United States." Houston reminded him to gather the "contingency sample," and Neil put some rocks and soil in his pocket. If, for any reason, the astronauts had to take off in a hurry, scientists back on Earth would get at least a pocketful of the Moon for their experiments.
Soon, Buzz joined him. "Beautiful view!" he exclaimed when he reached the lander's broad footpad. "Isn't that something!" agreed Armstrong. "Magnificent sight out here."
"Magnificent desolation," said Aldrin.
Those two words summed up the yin-yang of the Moon. The impact craters, the toppled boulders, the layers of moondust--it was utterly alien. Yet Tranquillity Base felt curiously familiar, like home. Later Apollo astronauts had similar feelings. Maybe this comes from staring at the Moon so often from Earth. Or maybe it's because the Moon is a piece of Earth, spun off our young planet billions of years ago. No one knows; it just is.
see caption
Above: Buzz Aldrin and the Eagle. 
Truly, much of the scene was weird. The airless landscape jumped out at the astronauts with disconcerting clarity and, as a result, the horizon felt unnaturally close. Worse yet, the whole world seemed to curve, a side-effect of the Moon's short thousand-mile radius. "Distances [here] are deceiving," noted Aldrin.
The sky was equally baffling. Although the Eagle had landed on a bright lunar morning, the sky was as black as midnight. An astronomer's paradise? No. Not a single star was visible. The glaring, sunlit ground ruined the astronaut's night vision. Only Earth itself was bright enough to be seen, luminous blue and white, hanging overhead.
Armstrong was particularly fascinated by moondust, which he kicked and scuffed with his boots. On Earth, kicking dust makes a little cloud in the air--but there is no air on the Moon. "When you kick the surface, [the dust goes out in] a little fan which, to me, is in the shape of a rose petal," recalls Armstrong. "There's just a little ring of particles--nothing behind 'em--no dust, no swirl, no nothing. It's really unique."

Enough of that. It was time for work.

Almost forgotten in Apollo lore are the checklists sewn to the forearms of the spacesuits. These "honey-do" memos from NASA were jam-packed with activities--from inspecting the lander to deploying the TV to collecting samples. Some of the tasks were as detailed as bending over and reporting to Mission Control how it went. They had a lot to do.
see captionNeil and Buzz deployed a solar wind collector, a seismometer and a laser retroreflector. They erected a flag and uncovered a plaque proclaiming, "We came in peace for all mankind." They took the first interplanetary phone call--"I just can't tell you how proud we all are," said President Nixon from the Oval Office. They collected 47 lbs of moon rocks and took 166 pictures. Check. Check. Check.
Right: Buzz Aldrin totes experiments from the Eagle onto the lunar surface. 
Finally, after two and a half busy, exhilarating hours, it was time to go. The checklist continued: Climb back in the Eagle. Stow the rocks. Prepare the ship for departure (again). Eat dinner: Beef stew or cream of chicken soup. And finally, sleep.
That was the limit. "You just are not going to get any sleep while you're waiting [for liftoff]," Aldrin said after the mission.
The Eagle was not a sleepy place. The tiny cabin was noisy with pumps and bright with warning lights that couldn't be dimmed. Even the window shades were glowing, illuminated by intense sunshine outside. "After I got into my sleep stage and all settled down, I realized there was something else [bothering me]," said Armstrong. The Eagle had an optical telescope sticking out periscope-style. "Earth was shining right through the telescope into my eye. It was like a light bulb."
To get some relief, they closed the helmets of their spacesuits. It was quiet inside and they "wouldn't be breathing all the dust" they had tramped in after the moon walk, said Aldrin. Alas, it didn't work. The suit's cooling systems, so necessary out on the scorching lunar surface, were too cold for sleeping inside the Eagle. The best Aldrin managed was a "couple hours of mentally fitful drowsing." Armstrong simply stayed awake.
When the wake-up call finally came,
"Tranquility Base, Tranquility Base, Houston. Over."
Armstrong answered with alacrity,
"Good morning, Houston. Tranquility Base. Over."
It was time to go home for a good night's sleep.