Hexbyte Glen Cove NASA's Mars helicopter's third flight goes farther, faster than before thumbnail

Hexbyte Glen Cove NASA’s Mars helicopter’s third flight goes farther, faster than before

Hexbyte Glen Cove

This NASA photo shows the Ingenuity Mars Helicopter(C) hovering during its third flight on April 25, 2021, as seen by the left Navigation Camera aboard NASA’s Perseverance Mars Rover

NASA’s mini helicopter Ingenuity on Sunday successfully completed its third flight on Mars, moving farther and faster than ever before, with a peak speed of 6.6 feet per second.

After two initial flights during which the craft hovered above the Red Planet’s surface, the helicopter on this third covered 64 feet (50 meters) of distance, reaching the speed of 6.6 feet per second (two meters per second), or four miles per hour in this latest flight.

“Today’s flight was what we planned for, and yet it was nothing short of amazing,” said Dave Lavery, the Ingenuity project’s program executive.

The Perseverance rover, which carried the four-pound (1.8 kilograms) rotorcraft to Mars, filmed the 80-second third flight. NASA said Sunday that would be sent to Earth in the coming days.

The lateral flight was a test for the helicopter’s autonomous navigation system, which completes the route according to information received beforehand.

“If Ingenuity flies too fast, the flight algorithm can’t track surface features,” NASA explained in a statement about the flight.

Ingenuity’s flights are challenging because of conditions vastly different from Earth’s—foremost among them a rarefied atmosphere that has less than one percent the density of our own.

This means that Ingenuity’s rotors, which span four feet, have to spin at 2,400 revolutions per minute to achieve lift—about five times more than a helicopter on Earth.

NASA announced it is now preparing for a fourth flight. Each flight is planned to be of increasing difficulty in order to push Ingenuity to its limits.

This black and white image was taken by NASA’s Ingenuity helicopter during its third flight on April 25, 2021. Credit:  NASA/JPL-Caltech

The Ingenuity experiment will end in one month in order to let Perseverance return to its main task: searching for signs of past microbial life on Mars.



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NASA’s Mars helicopter’s third flight goes farther, faster than before (2021, April 25)
retrieved 26 April 2021
from https://phys.org/news/2021-04-nasa-mars-helicopter-flight-faster.html

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Hexbyte Glen Cove Evolution favors new diseases of 'intermediate' severity thumbnail

Hexbyte Glen Cove Evolution favors new diseases of ‘intermediate’ severity

Hexbyte Glen Cove

Credit: CC0 Public Domain

New epidemic diseases have an evolutionary advantage if they are of “intermediate” severity, research shows.

Scientists tested the theory that (disease-causing organisms) that inflict intermediate levels of harm on their host are the most evolutionarily successful.

The study, by the University of Exeter, Arizona State University and Auburn University, found that natural selection favors pathogens of intermediate (how much harm a pathogen causes) at the point the disease emerges in a new host species.

This occurs because virulence and transmission are linked, with virulence arising because pathogens need to exploit hosts to persist, replicate and transmit.

While too-low virulence will be detrimental for pathogens if they cannot transmit, virulence that is too high will also be a disadvantage if infection kills hosts so fast that the pathogen does not have time to transmit.

Over time, pathogens that show intermediate levels of virulence should therefore have an .

“For a long time, conventional wisdom held that new diseases evolved to become harmless,” said Dr. Camille Bonneaud, of the Centre for Ecology and Conservation on Exeter’s Penryn Campus in Cornwall.

“Although theoretical developments in evolutionary biology in the 1980s showed that this was not necessarily the case, such belief still holds firm, even today.

“Our study focussed on the ‘virulence-transmission trade-off’ hypothesis, which allows us to make predictions about pathogen evolution.

“Experimental evidence for this theory is rare, but we were able to test it by using more than 50 variants of the infectious bacterial pathogen Mycoplasma gallisepticum, which infects house finches.”

In the study, house finches from populations that had never encountered the disease were exposed to one of the different variants, simulating conditions at epidemic outbreak.

“We found that variants that were more virulent transmitted faster, but that variants of intermediate virulence were the most evolutionarily successful,” Dr. Bonneaud said.

“Our results therefore provide support for using the virulence-transmission trade-off hypothesis as a framework for understanding and predicting emerging pathogen evolution.”

Counter to commonly held beliefs, however, variants of the pathogen that replicated faster during infection and achieved higher densities did not transmit better or faster than those that achieved lower densities.

“This tells us that transmission is not always a numbers game and that we cannot use pathogen numbers as a proxy for their success.”

The paper, published in the journal Evolution Letters, is entitled: “Experimental evidence for stabilizing selection on virulence in a bacterial pathogen.”



More information:
Camille Bonneaud et al, Experimental evidence for stabilizing selection on virulence in a bacterial pathogen, Evolution Letters (2020). DOI: 10.1002/evl3.203

Citation:
Evolution favors new diseases of ‘intermediate’ severity (2020, November 12)
retrieved 12 November 2020
from https://phys.org/news/2020-11-evolution-favors-diseases-intermediate-severity.html

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