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New model challenges idea that Pluto started out frozen – Ars Technica

Young Pluto —

Surface images used to test “cold start” vs. “hot start” ideas.


New model challenges idea that Pluto started out frozen

Pluto’s recategorization as a dwarf planet may have caused some past anger, but there has never been a better time to be a Pluto fan. Since the New Horizons mission gave us our first real look at Pluto in 2015, researchers have been digging into the rich reality of this icy world. The latest question under the magnifying glass: what was Pluto like at its birth?

Beneath its surface—composed of frozen water, nitrogen, carbon monoxide, and more—Pluto is today thought to have a liquid water ocean surrounding a rocky core. But scientists are trying to figure out how long it has been that way. In the “cold start” model, Pluto’s interior ocean is thought to have been frozen but then gradually thawed due to heat from radioactive decay in the core. But it remains possible that a “hot start” model is more accurate, one where the planet started out warm enough to form some liquid water.

Cold start vs. hot start

Although the dwarf planet’s beginnings are buried deep in the past, its two possible origins should have left marks on the surface.

The key is to think about the fact that water expands when it freezes and contracts when it melts. Just as the skin of a balloon stretches when inflated, Pluto’s exterior would have to contract or expand as its interior melted or froze. A cold start with an initially frozen interior “ocean” would cause contraction as it thawed, generating compression along the surface. But after a while, the heat provided by radioactive decay in the core would diminish enough that the loss of heat to space would win out, causing the interior ocean to start freezing again. That would result in expansion, causing extension along Pluto’s surface.

A “hot start”, on the other hand, would see a liquid interior ocean from the start. There would be a rapid phase of cooling and freezing early on, generating extension on the surface. Then the radioactive-decay heating from the core and cooling from the surface would come closer to balance, greatly slowing the freezing rate for the rest of Pluto’s lifetime but still continuing the surface extension.

Here is what the two models predict for Pluto's surface over its history. (

Enlarge / Here is what the two models predict for Pluto’s surface over its history. (“Gyr” means billions of years.)

So by analyzing the visible faults on Pluto’s surface and noting how they’ve moved, it should be possible to differentiate between compression-then-extension and extension-only versions of Pluto’s history. UC Santa Cruz’s Carver Bierson and Francis Nimmo, along with New Horizons lead Alan Stern, put this idea to the test using what we’ve learned about Pluto’s geology.

As it happens, the researchers say there’s no evidence of compression to be seen. There are, however, relatively recent extension faults, which often produce a sunken valley between pairs of faults. So perhaps the “hot start” model is closer to reality than the more popular “cold start” hypothesis.

Fast assembly required

There’s also a very old-looking topographical feature that may represent some extension. Although there isn’t a complete and rigorous estimate of the amount of extension recorded by all these faults, the researchers’ rough calculation is compatible with their “hot start” model for Pluto’s history.

There are, theoretically, ways that the available evidence could be misleading. Faults that form under compression can reverse direction under extension later, for one. And it’s possible that impact events (particularly the one that formed Pluto’s moon Charon) and other surface processes could have erased or hidden evidence of compression. Still, all the observable geology seems to point to the “hot start” explanation.

How is it that an icy world in the outer reaches of the Solar System starts out warm, you ask? It has to do with the assembly of Pluto from the smaller pieces swirling around during the formation of the Solar System. As pieces were pulled in by gravitational attraction, energy was converted to heat on impact. So as long as Pluto assembled quickly enough to gain that heat faster than it shed heat to space, its interior could reach high temperatures.

The researchers ran the numbers and found that assembly times of around 30,000 years would definitely hit the required temperatures—though if Pluto formed from bigger chunks (which collect heat more efficiently), that number could stretch to a few million years.

Some of the models used to simulate the processes that assembled our Solar System take considerably longer than that, but some newer models can put a Pluto together quickly enough. The requirement of rapid assembly is, at the least, not a problem for the “hot start” idea.

The researchers suggest another way to test their hypothesis further, though: a much better estimate of the amount of extension Pluto’s surface has undergone would make it clearer which model is the winner.

Nature Geoscience, 2020. DOI: 10.1038/s41561-020-0595-0 (About DOIs).

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Coronavirus Model

Coronavirus model once used by White House now predicts 200,000 U.S. deaths by October – CBS News

A coronavirus model once used by the White House now projects more than 200,000 Americans could die of COVID-19 by October 1. The prediction went up by more than 30,000 since last week. 

As of Tuesday, more than 116,000 people in the U.S. have died of the coronavirus, and the death toll is still growing by hundreds per day. Infection rates and hospitalizations are rising in numerous states as businesses open up and people drop precautions.

According to the latest model from the Institute for Health Metrics and Evaluation at the University of Washington, a research institute once utilized by the White House for coronavirus projections, another 85,000 or so deaths are now projected by October 1.

IHME’s interactive projections show that by October 1, deaths from the coronavirus in the United States could reach anywhere from 171,000 to 270,000, with a likely figure in between of about 201,129. Daily deaths from the coronavirus are expected to begin rising again in September, after they started to plateau nationwide this month for the first time.

According to the IHME, “rising mobility and premature relaxation of social distancing in some states are the main reasons” for the projected increase.

ihme-oct1-covid-deaths.jpg
This chart from the Institute for Health Metrics and Evaluation shows the projection for total U.S. deaths from COVID-19 through October 1, 2020.

Institute for Health Metrics and Evaluation


IHME Director Dr. Christopher Murray explained the reasons behind the upward trend at a June 11 press briefing, before the institute raised its projections again this week.

“Starting in the third week of August in our forecast at the national level, we see the daily death rate… going up again, after having been declining since mid-April at the national level,” he said. “That increase in daily deaths really starts to gather momentum from mid-September onwards.”

“What’s underlying that is two factors: The steady rise in contact rates, steady rise in mobility, and the likely continued relaxation of mandates over the course of the summer. Combined with the increasingly clear signal that seasonality is important,” he said. 

According to the IHME, “Higher mobility means higher transmission and more infections at the beginning of the expected second wave” in the fall. 

As COVID-19 cases continue to decline in New York, once the epicenter of the nation’s outbreak, new hotspots are emerging in states across the South and Southwest. Some health experts say we could be seeing the impact of reopening too early. 

To account for the unpredictability of states where hotspots are emerging, the IHME’s projection includes a wide range of outcomes, according to Murray. “Part of that range is just quite making sense of what’s happening in some of the states such as Arizona, where we see an upsurge in hospitalizations and cases and deaths,” he said. 

Arizona is seeing more than 1,000 new cases per day, up from fewer than 400 a day in mid-May when stay-at-home orders were eased.

“I think the question of did we open too soon is a valid one,” Frank Lovecchio, an emergency medicine doctor in the Phoenix area, told CBS News’ Michael George. Lovecchio said he’s seen a surge of severe cases requiring intubation.

Murray said IHME adjusted its projections based on a variety of data on people’s self-reported numbers of contacts, as well as contextual factors like smoking, air pollution and use of face masks. He called mask use “an important contributor” to their modeling. 

The Centers for Disease Control and Prevention issued updated guidelines on Friday to help people minimize their everyday risk of contracting the virus, and emphasized that wearing masks can help. 

“It’s important that you and the people around you wear a cloth face covering when in public and particularly when it’s difficult to stay 6 feet away from others consistently,” the CDC said. It also advised people to bring their own food and drinks to cookouts, wave instead of hug, take the stairs instead of elevators, and sanitize hands after using ATMs. 

In his briefing, Murray pointed out that the IHME’s projections are based on many different factors, and the public’s behavior can make a big difference in the final outcome.

“We’re making a forecast, clearly what individuals choose to do can moderate that forecast,” Murray said. “If mask use starts to go back up in states where it’s not very high, that is likely to be very helpful. And if people avoid contacts with people outside their household… that will also moderate the effect.”

He added that these safety measures “will become even more important in the fall when the effect of seasonality is to drive up transmission.”

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Model Tesla

Tesla Model 3 becomes best-selling car in California, first electric to top the list – Fox News

City unveils gigantic Elon Musk statue in bid to lure Tesla to town

Tulsa, Oklahoma, has given its landmark 75-foot-tall Golden Driller statue an extreme makeover. The Tesla Owners of Oklahoma organized the redesign of the statue to resemble the likeness of Tesla CEO, Elon Musk. The stunt is all a part of Tulsa’s attempt to be selected as the site for Tesla’s second U.S. automotive manufacturing facility.

Tesla CEO Elon Musk may have had his issues with California’s government officials over their handling of the coronavirus crisis, but things couldn’t have been better with the state’s car buyers early this year.

David Paul Morris/Bloomberg via Getty Images

David Paul Morris/Bloomberg via Getty Images

According to the California New Car Dealers Association, the Tesla Model 3 was the best-selling vehicle in the state during the first quarter of 2018, marking the first time an electric car topped the list.

Data collected by the association found that 18,853 Model 3s were registered during the period, with the Honda Civic a close second at 18,001. The Toyota Camry, Toyota Rav4 and Honda Accord rounded out the top five. Tesla does not release sales results for individual states and countries, but said it delivered a combined 76,200 of the Model 3 and related Model Y utility vehicle globally during the first three months of the year.

ELON MUSK SAYS FULL-SELF DRIVING CAPABILITY WILL BE WORTH $100,000

Tesla, which only sells three models, also gained market share, jumping from 4.0 to 4.6 percent, while Toyota remained in first with 17 percent, ahead of Honda at 11.1 percent.

Behind the Model 3, the best selling vehicles from American brands were the Ford F-Series (12,981), Chevrolet Silverado (11,896), and Ram (11,858) pickups.

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