18-ton section of Chinese rocket crash lands following uncontrolled reentry

If you were awaiting screaming death from the skies, you can relax. For now.

China's Long March 5 (CZ-5B) rocket on the way up.

Image source: STR/Getty Images
  • China's Long March 5 rocket core has landed safely in the Atlantic Ocean following an uncontrolled entry.
  • Most of the time, returning hardware that doesn't burn up plunges into the ocean or uninhabited areas.
  • There have been two larger returnees in the past, though this one was quite big.

Maybe future generations will look back on these early days of space exploration and chuckle at what we had to suffer through. We live in a time when, every now and then, word goes out that some giant chunk of uncontrolled defunct space junk is about to crash down upon us somewhere, so, um, duck? The hope during such moments is that the deadly debris will land in the ocean that covers most of the Earth's surface or in some unpopulated area, and it usually does. Usually.

Anyhow, if you've been anxiously looking up this week — either at the sky or your ceiling in quarantine — waiting for the core section of China's Long March 5 (CZ-5B) rocket to end you, you can breathe a sigh of relief. It landed safely, for humans anyway, in the ocean off the west coast of Mauritania in northwest Africa on May 11.

Long March into the sea

Though CZ-5B is one of the largest craft to come down in an uncontrolled reentry, its size is not the only thing that had astronomers like Jonathan McDowell, of the Harvard-Smithsonian Center for Astrophysics, on the edge of their seats. "I've never seen a major reentry pass directly over so many major conurbations!" he tweeted. (A conurbation is an extended urban area.)

While some debris comes down via a controlled landing, that was not the plan for CZ-5B. McDowell tells CNN, "For a large object like this, dense pieces like parts of the rocket engines could survive reentry and crash to Earth." No biggie, he says, since, "Once they reach the lower atmosphere they are traveling relatively slowly, so worst case is they could take out a house."

CZ-5B took off just a week or so ago, on May 5 for just a few days in orbit. Some of its 30-meter-long core stage burned up on reentry, and apparently none of what remained hit anyone, but there are reports of property damage in the Côte d'Ivoire village of N'guinou.

We’ve ducked debris before

A no-doubt radioactive piece of Cosmos 954

Image source: Natural Resources Canada/Wikimedia

At this point, there have been a number of well-publicized spacecraft plummeting down destination-unknown. Probably the scariest was the return of the 4.4-ton Soviet-era spy satellite Cosmos 954. What made its uncontrolled re-entry so frightening is that it was nuclear-powered and threatened to spew radioactive material all over wherever or whomever. The original plan had been to boost it high into a nuclear-safe orbit, but a separation failure doomed the craft to fall back to Earth.

In the end, Cosmos 954 did crash in Northwestern Canada, blowing radioactive debris over a wide area. Canada billed the U.S.S.R $6 million for the cleanup, of which only $3 million was eventually paid.

Probably the first widely publicized uncontrolled return, and one of the two most massive, was of Skylab in 1979. It was another case of a craft coming back earlier than intended, and though NASA couldn't control the 77-ton craft's reentry point, it could control the manner in which it tumbled on down. The nail-biting ended on July 11, 1979, when most of Skylab burned up over the Indian Ocean, though some big pieces survived the descent and landed southeast of Perth, Australia. No one got hurt. The Australian town of Esperance charged NASA $400 for littering. The U.S. also didn't pay up.

Another piece of debris larger than CZ-5B was the Soviet Salyut 7 after nine years in orbit. At the time it came down, it was docked with another spaceship, Cosmos 1686. Salyut 7 weighted in at about 22 tons, as did Cosmos 1686. The connected pair of craft reentered together, burning up and breaking apart over Argentina, with bits raining down on the town of Capitan Bermudez. Amazingly, no one was injured.

One could say we've been pretty lucky so far, though it's hard not to look forward to a time when dying spacecraft can be somehow vaporized out in space where it's safe instead putting those of us down here at absolutely-nothing-you-can-do-about-it risk.

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Photos: Courtesy of Let Grow
Sponsored by Charles Koch Foundation
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The surprise reason sleep-deprivation kills lies in the gut

New research establishes an unexpected connection.

Reactive oxygen species (ROS) accumulate in the gut of sleep-deprived fruit flies, one (left), seven (center) and ten (right) days without sleep.

Image source: Vaccaro et al, 2020/Harvard Medical School
Surprising Science
  • A study provides further confirmation that a prolonged lack of sleep can result in early mortality.
  • Surprisingly, the direct cause seems to be a buildup of Reactive Oxygen Species in the gut produced by sleeplessness.
  • When the buildup is neutralized, a normal lifespan is restored.

We don't have to tell you what it feels like when you don't get enough sleep. A night or two of that can be miserable; long-term sleeplessness is out-and-out debilitating. Though we know from personal experience that we need sleep — our cognitive, metabolic, cardiovascular, and immune functioning depend on it — a lack of it does more than just make you feel like you want to die. It can actually kill you, according to study of rats published in 1989. But why?

A new study answers that question, and in an unexpected way. It appears that the sleeplessness/death connection has nothing to do with the brain or nervous system as many have assumed — it happens in your gut. Equally amazing, the study's authors were able to reverse the ill effects with antioxidants.

The study, from researchers at Harvard Medical School (HMS), is published in the journal Cell.

An unexpected culprit

The new research examines the mechanisms at play in sleep-deprived fruit flies and in mice — long-term sleep-deprivation experiments with humans are considered ethically iffy.

What the scientists found is that death from sleep deprivation is always preceded by a buildup of Reactive Oxygen Species (ROS) in the gut. These are not, as their name implies, living organisms. ROS are reactive molecules that are part of the immune system's response to invading microbes, and recent research suggests they're paradoxically key players in normal cell signal transduction and cell cycling as well. However, having an excess of ROS leads to oxidative stress, which is linked to "macromolecular damage and is implicated in various disease states such as atherosclerosis, diabetes, cancer, neurodegeneration, and aging." To prevent this, cellular defenses typically maintain a balance between ROS production and removal.

"We took an unbiased approach and searched throughout the body for indicators of damage from sleep deprivation," says senior study author Dragana Rogulja, admitting, "We were surprised to find it was the gut that plays a key role in causing death." The accumulation occurred in both sleep-deprived fruit flies and mice.

"Even more surprising," Rogulja recalls, "we found that premature death could be prevented. Each morning, we would all gather around to look at the flies, with disbelief to be honest. What we saw is that every time we could neutralize ROS in the gut, we could rescue the flies." Fruit flies given any of 11 antioxidant compounds — including melatonin, lipoic acid and NAD — that neutralize ROS buildups remained active and lived a normal length of time in spite of sleep deprivation. (The researchers note that these antioxidants did not extend the lifespans of non-sleep deprived control subjects.)

fly with thought bubble that says "What? I'm awake!"

Image source: Tomasz Klejdysz/Shutterstock/Big Think

The experiments

The study's tests were managed by co-first authors Alexandra Vaccaro and Yosef Kaplan Dor, both research fellows at HMS.

You may wonder how you compel a fruit fly to sleep, or for that matter, how you keep one awake. The researchers ascertained that fruit flies doze off in response to being shaken, and thus were the control subjects induced to snooze in their individual, warmed tubes. Each subject occupied its own 29 °C (84F) tube.

For their sleepless cohort, fruit flies were genetically manipulated to express a heat-sensitive protein in specific neurons. These neurons are known to suppress sleep, and did so — the fruit flies' activity levels, or lack thereof, were tracked using infrared beams.

Starting at Day 10 of sleep deprivation, fruit flies began dying, with all of them dead by Day 20. Control flies lived up to 40 days.

The scientists sought out markers that would indicate cell damage in their sleepless subjects. They saw no difference in brain tissue and elsewhere between the well-rested and sleep-deprived fruit flies, with the exception of one fruit fly.

However, in the guts of sleep-deprived fruit flies was a massive accumulation of ROS, which peaked around Day 10. Says Vaccaro, "We found that sleep-deprived flies were dying at the same pace, every time, and when we looked at markers of cell damage and death, the one tissue that really stood out was the gut." She adds, "I remember when we did the first experiment, you could immediately tell under the microscope that there was a striking difference. That almost never happens in lab research."

The experiments were repeated with mice who were gently kept awake for five days. Again, ROS built up over time in their small and large intestines but nowhere else.

As noted above, the administering of antioxidants alleviated the effect of the ROS buildup. In addition, flies that were modified to overproduce gut antioxidant enzymes were found to be immune to the damaging effects of sleep deprivation.

The research leaves some important questions unanswered. Says Kaplan Dor, "We still don't know why sleep loss causes ROS accumulation in the gut, and why this is lethal." He hypothesizes, "Sleep deprivation could directly affect the gut, but the trigger may also originate in the brain. Similarly, death could be due to damage in the gut or because high levels of ROS have systemic effects, or some combination of these."

The HMS researchers are now investigating the chemical pathways by which sleep-deprivation triggers the ROS buildup, and the means by which the ROS wreak cell havoc.

"We need to understand the biology of how sleep deprivation damages the body so that we can find ways to prevent this harm," says Rogulja.

Referring to the value of this study to humans, she notes,"So many of us are chronically sleep deprived. Even if we know staying up late every night is bad, we still do it. We believe we've identified a central issue that, when eliminated, allows for survival without sleep, at least in fruit flies."

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Photo Illustration by Joe Raedle/Getty Images
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