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A new approach to flagship space telescopes – The Space Review

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The astrophysics decadal survey recommended a scaled-down version of a space telescope concept called LUVOIR as the first in a line of flagship space observatories to be developed over the next few decades. (credit: NASA/GSFC)

For much of this year, the biggest puzzle for astrophysicists had nothing to do with dark matter, dark energy, or discrepancies in the value of the Hubble Constant. Instead, the question at the top of their minds was: when was Astro2020 coming out?

Astro2020 was the shorthand for the latest astrophysics decadal survey, the once-a-decade review of the state of the field and recommendations for both ground- and space-based projects to pursue to answer the top scientific questions. The final report by the decadal survey’s steering committee, once expected in late 2020 as the name suggests, had slipped to some time in 2021 because of the pandemic, which forced a shift from in-person to virtual meetings just as work on the survey was going into high gear.

The decision to pick a concept between LUVOIR and HabEx was driven by science and budgets: big enough to do meet key science objectives like characterizing exoplanets, but also small enough to fit into a reasonable cost and schedule.

The committee itself kept quiet about its work, providing little specific guidance about when to expect the final report. At a meeting of NASA’s Astrophysics Advisory Committee in October, Paul Hertz, director of the agency’s astrophysics division, presented the results of an office pool from earlier in the year predicting when the report would be released. All but two thought the report would have already been released by the mid-October meeting of that committee; those two predicted it would be released the week of Thanksgiving.

Fortunately, they and the rest of the astrophysics community did not have to wait until last week’s holiday to get their hands on the report. The document, released November 4, provided astronomers with a long-awaited roadmap for not just the next decade but arguably through the middle of the century, endorsing a set of observatories that can peer back into the distant early universe and also look for habitable worlds close to home.

While the decadal survey makes a series of recommendations for smaller missions and ground-based telescopes, what gets the most attention is its recommendation for a large strategic, or flagship, space mission. That recommendation is just that—NASA isn’t bound to accept it—yet the agency has adopted the top-ranked flagship missions of previous decadals. That includes the one picked in the previous decadal in 2010, which became the Wide-Field Infrared Survey Telescope (WFIRST), renamed by NASA to the Nancy Grace Roman Space Telescope last year.

NASA, in preparation for Astro2020, commissioned detailed studies of four proposed flagship observatories, operating from far infrared to X-ray wavelengths (see “Selecting the next great space observatory”, The Space Review, January 21, 2019.) These studies offered detailed technical, scientific, and budgetary information for the concepts, which were effectively finalists for the being the next flagship mission—although the decadal survey was not under any obligation to pick one.

And, in the end, they didn’t pick one of the four. Instead, the recommended flagship mission was something of a compromise between two of the concepts. One, the Habitable Exoplanet Observatory, or HabEx, proposed a space telescope between 3.2 and 4 meters across optimized to search for potentially habitable exoplanets. The other, the Large Ultraviolet Optical Infrared Surveyor, or LUVOIR, proposed a large space telescope between 8 and 15 meters across for use in a wide range of astrophysics, from exoplanet studies to cosmology.

What the decadal recommended was a telescope six meters across capable of observations in ultraviolet, visible, and infrared wavelengths: similar to LUVOIR but scaled down to a size between the smaller version of LUVOIR and HabEx.

The decision to pick a concept between LUVOIR and HabEx was driven by science and budgets: big enough to do meet key science objectives like characterizing exoplanets, but also small enough to fit into a reasonable cost and schedule. “We thought that six meters provides assurance of enough target planets, but it’s also a big enough gain in capability over Hubble to really enable general astrophysics,” said Robert Kennicutt, an astronomer at the University of Arizona and Texas A&M University who was one of the two co-chairs of the decadal survey committee.

“We realized that all of these are visionary ideas but they require timelines that are pan-decadal, even multi-generational,” said Harrison. “We really think a different approach needs to be taken.”

That telescope—not given a name by the decadal survey—will still be expensive and take a long time to build. The decadal’s estimates, which included independent cost and schedule analyses, projected the telescope would cost $11 billion to build, in line with the James Webb Space Telescope when accounting for inflation, and be ready for launch in the first half of the 2040s. But the original LUVOIR concept would have cost $17 billion and not be ready until the 2050s, according to those same analyses. HabEx, the decadal survey concluded, would have been cheaper but too small to meet many of those science goals.

That selection of a flagship mission was, alone, not that different than past decadal surveys. Even that compromise pick is not unprecedented, as the previous decadal’s recommendation of what would become Roman emerged from combining several concepts. What was different, though, was the realization that, after the delays and cost overruns suffered by past flagships, notably the James Webb Space Telescope, NASA needed a different approach to developing such missions.

“We realized that all of these are visionary ideas but they require timelines that are pan-decadal, even multi-generational,” said Fiona Harrison of Caltech, the other co-chair of the steering committee, referring to the four flagship concepts studied for the decadal. “We really think a different approach needs to be taken.”

What the decadal survey recommended was that the space telescope it recommended be just the first mission to emerge from a new Great Observatories Mission and Technology Maturation Program at NASA. That program would mature technologies for a series of flagship missions in a coherent fashion.

“The survey committee expects that this process will result in decreased cost and risk and enable more frequent launches of flagship missions, even if it does require significantly more upfront investment prior to a decadal recommendation regarding implementation,” the committee concluded in the report.

Specifically, it recommended that, five years after starting work on the large space telescope that was the report’s top priority, NASA begin studies of two other flagship missions, a far infrared space telescope and an X-ray observatory, at estimated costs of $3–5 billion each. Both are similar to the other two flagship mission concepts studied by NASA for this decadal survey, the Origins Space Telescope and Lynx X-ray Observatory.

Setting up studies of those future mission concepts, without committing to them, allows NASA to adapt if both technologies or science goals change, another member of the decadal survey steering committee noted. “If the progress appears to be stalled or delayed, then we can rapidly onramp another one of the compelling, exciting ideas,” said Keivan Stassun of Vanderbilt University. “We can be phasing in multiple great ideas.”

“We were tasked and encouraged by the funding agencies, including NASA, to really think big, bold, ambitious, and long-term,” Stassun said.

The idea that it takes a long time to develop flagship space telescopes is not new: the first studies of JWST, originally called the Next Generation Space Telescope, predate the launch of the Hubble Space Telescope more than three decades ago, and that spacecraft is only now about to launch. But the study’s proposal recognizes that the problems experienced by JWST and, to a lesser extent, Roman, require a different approach to managing such complex, expensive missions.

It also reflects the realization that some of the questions that astrophysics is seeking to answer can’t be easily fit into decade-long timeframes. “We were tasked and encouraged by the funding agencies, including NASA, to really think big, bold, ambitious, and long-term,” Stassun said. “We took that to mean that we should not be thinking only about that which can be accomplished in a ten-year period.”

NASA’s Hertz had, in fact, urged the decadal survey to be bold on many occasions before and during its deliberations. “I asked the decadal survey to be ambitious, and I believe they are certainly ambitious,” he said at a November 8 meeting of the Committee on Astronomy and Astrophysics of the National Academies’ Space Studies Board.

NASA is only starting to review the overall recommendations of the decadal, he said. That includes not just its analysis of flagship missions but endorsement of a new medium-class line of “probe” missions, with a cost of $1.5 billion per mission and flying once a decade. Such missions would be analogous to the New Frontiers line of planetary science missions that fall between planetary science flagships and smaller Discovery class missions.

The delay in completing the decadal means it won’t have an impact on NASA’s next budget proposal for fiscal year 2023, which is already in active development for release in early 2022. Hertz said he’ll provide some initial comment on the decadal at a town hall meeting during the American Astronomical Society meeting in early January, particularly any recommendations that can be accommodated in the fiscal year 2022 budget. A complete, formal response will come later next year after a series of town hall meetings.

Those plans will depend on budgets. The first views Congress has on the decadal, including its flagship mission plans, will come Wednesday when the House Science Committee’s space subcommittee holds a hearing on the report.

Hertz was optimistic in general about the state of NASA’s astrophysics programs, citing the impending launch of JWST and Roman passing its critical design review. “I’m really excited. This is a great time for astrophysics,” he said. Astronomers hope the decadal’s recommendations, if implemented, can make it a great few decades for the field.


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Ancient life may be just one possible explanation for Mars rover's latest discovery – CTV News

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In the search for life beyond Earth, NASA’s Curiosity rover has been on a nearly decade-long mission to determine if Mars was ever habitable for living organisms.

A new analysis of sediment samples collected by the rover revealed the presence of carbon — and the possible existence of ancient life on the red planet is just one potential explanation for why it may be there.

Carbon is the foundation for all of life on Earth, and the carbon cycle is the natural process of recycling carbon atoms. On our home planet, carbon atoms go through a cycle as they travel from the atmosphere to the ground and back to the atmosphere. Most of our carbon is in rocks and sediment and the rest is in the global ocean, atmosphere and organisms, according to NOAA, or the National Oceanic and Atmospheric Administration.

That’s why carbon atoms — with their cycle of recycling — are tracers of biological activity on Earth. So they could be used to help researchers determine if life existed on ancient Mars.

When these atoms are measured inside another substance, like Martian sediment, they can shed light on a planet’s carbon cycle, no matter when it occurred.

Learning more about the origin of this newly detected Martian carbon could also reveal the process of carbon cycling on Mars.

A study detailing these findings published Monday in the journal Proceedings of the National Academy of Sciences.

SECRETS IN THE SEDIMENT

Curiosity landed in Gale Crater on Mars in August 2012. The 154.5-kilometre crater, named for Australian astronomer Walter F. Gale, was probably formed by a meteor impact between 3.5 billion and 3.8 billion years ago. The large cavity likely once held a lake, and now it includes a mountain called Mount Sharp. The crater also includes layers of exposed ancient rock.

For a closer look, the rover drilled to collect samples of sediment across the crater between August 2012 and July 2021. Curiosity then heated these 24 powder samples to around 1,562 degrees Fahrenheit (850 degrees Celsius) in order to separate elements. This caused the samples to release methane, which was then analyzed by another instrument in the rover’s arsenal to show the presence of stable carbon isotopes, or carbon atoms.

Some of the samples were depleted in carbon while others were enriched. Carbon has two stable isotopes, measured as either carbon 12 or carbon 13.

“The samples extremely depleted in carbon 13 are a little like samples from Australia taken from sediment that was 2.7 billion years old,” said Christopher H. House, lead study author and professor of geosciences at Pennsylvania State University, in a statement.

“Those samples were caused by biological activity when methane was consumed by ancient microbial mats, but we can’t necessarily say that on Mars because it’s a planet that may have formed out of different materials and processes than Earth.”

In lakes on Earth, microbes like to grow in big colonies that essentially form mats just under the surface of the water.

THREE POSSIBLE CARBON ORIGINS

The varied measurements of these carbon atoms could suggest three very different things about ancient Mars. The origin of the carbon is likely due to cosmic dust, ultraviolet degradation of carbon dioxide, or the ultraviolet degradation of biologically produced methane.

“All three of these scenarios are unconventional, unlike processes common on Earth,” according to the researchers.

The first scenario involves our entire solar system passing through a galactic dust cloud, something that occurs every 100 million years, according to House. The particle-heavy cloud could trigger cooling events on rocky planets.

“It doesn’t deposit a lot of dust,” House said. “It is hard to see any of these deposition events in the Earth record.”

But it’s possible that during an event like this, the cosmic dust cloud would have lowered temperatures on ancient Mars, which may have had liquid water. This could have caused glaciers to form on Mars, leaving a layer of dust on top of the ice. When the ice melted, the layer of sediment including carbon would have remained. While it’s entirely possible, there is little evidence for glaciers in Gale Crater and the study authors said it would require further research.

The second scenario involves the conversion of carbon dioxide on Mars into organic compounds, such as formaldehyde, due to ultraviolet radiation. That hypothesis also requires additional research.

The third way this carbon was produced has possible biological roots.

If this kind of depleted carbon measurement was made on Earth, it would show that microbes were consuming biologically produced methane. While Curiosity has previously detected methane on Mars, researchers can only guess if there were once large plumes of methane being released from beneath the surface of Mars. If this was the case and there were microbes on the Martian surface, they would have consumed this methane.

It’s also possible that the methane interacted with ultraviolet light, leaving a trace of carbon on the Martian surface.

MORE DRILLING ON THE HORIZON

The Curiosity rover will be returning to the site where it collected the majority of the samples in about a month, which will allow for another chance to analyze sediment from this intriguing location.

“This research accomplished a long-standing goal for Mars exploration,” House said. “To measure different carbon isotopes — one of the most important geology tools — from sediment on another habitable world, and it does so by looking at nine years of exploration.”

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Mars Was Likely A Cold, Wet World 3 Billion Years Ago – IFLScience

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Mars is puzzling. From rover and satellite observations we know that it once had plenty of water on its surface, which usually suggests warm and wet conditions. On the other hand, evidence suggests the planet was always pretty chilly, even in the distant past, but it’s not a cold, dry desert either. These two ideas are often at odds, but new research suggests that they could both be true: ancient Mars was likely a frigid world both cold and wet.

Researchers set out to create a model that can explain the perplexing features witnessed on the Red Planet. If the planet wasn’t warm and wet or cold and dry could there be a third option? Publishing their findings in Proceedings of the National Academy of Sciences, they believe that their cold and wet scenario can explain the existence of a vast liquid ocean in the Northern Hemisphere of Mars, extending to its polar region.

However, the model needed to explain both the presence of a liquid ocean and ice-capped regions, like the presence of glacial valleys and ice sheets in the southern highlands.

Planetary scientists studying Mars have found evidence of ancient tsunamis that rocked the Red Planet. If the ocean was frozen due to a very cold climate, these tsunamis would not have happened. But a milder climate would have meant transferring water from the ocean to the land through precipitation. Cold and wet conditions, however, could have existed.

The team used an advanced general circulation model to work out the necessary parameters for this world. They calculated it was possible for an ocean to be stable even if the mean temperature of Mars was below 0°C (32°F), the freezing point of water, 3 billion years ago. They envisioned ice-covered plateaus in the south with glaciers flowing across the plains and returning to the ocean. Rainfall would have been moderate around the shoreline. In this scenario, the ocean surface could be up to 4.5°C (40°F); not tropical but enough for water to stay liquid.

The key to these conditions is all in the air. The atmosphere of Mars today is about 1 percent in density compared to Earth’s own. But, if in the past it was roughly the same and was made of about 10 percent hydrogen and the rest carbon dioxide, this scenario would actually work. Previous analyses have found strong evidence for a thicker atmosphere before it was ripped from the planet by the steady stream of particles from the Sun.

The model is certainly compelling in explaining the peculiarities of Mars, but of course, much more evidence is needed to understand what the Red Planet was really like billions of years ago.

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Explainer-Scientists struggle to monitor Tonga volcano after massive eruption

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Scientists are struggling to monitor an active volcano that erupted off the South Pacific island of Tonga at the weekend, after the explosion destroyed its sea-level crater and drowned its mass, obscuring it from satellites.

The eruption of Hunga-Tonga-Hunga-Ha’apai volcano, which sits on the seismically active Pacific Ring of Fire, sent tsunami waves across the Pacific Ocean and was heard some 2,300 kms (1,430 miles) away in New Zealand.

“The concern at the moment is how little information we have and that’s scary,” said Janine Krippner, a New Zealand-based volcanologist with the Smithsonian Global Volcanism Program.

“When the vent is below water, nothing can tell us what will happen next.”

Krippner said on-site instruments were likely destroyed in the eruption and the volcanology community was pooling together the best available data and expertise to review the explosion and predict anticipated future activity.

Saturday’s eruption was so powerful that space satellites captured not only huge clouds of ash but also an atmospheric shockwave that radiated out from the volcano at close to the speed of sound.

Photographs and videos showed grey ash clouds billowing over the South Pacific and metre-high waves surging onto the coast of Tonga.

There are no official reports of injuries or deaths in Tonga https://www.reuters.com/business/environment/impact-assessment-aid-efforts-underway-world-responds-tonga-tsunami-2022-01-16 yet but internet and telephone communications are extremely limited and outlying coastal areas remain cut off.

Experts said the volcano, which last erupted in 2014, had been puffing away for about a month before rising magma, superheated to around 1,000 degrees Celsius, met with 20-degree seawater on Saturday, causing an instantaneous and massive explosion.

The unusual “astounding” speed and force of the eruption indicated a greater force at play than simply magma meeting water, scientists said.

As the superheated magma rose quickly and met the cool seawater, so did a huge volume of volcanic gases, intensifying the explosion, said Raymond Cas, a professor of volcanology at Australia’s Monash University.

Some volcanologists are likening the eruption to the 1991 Pinatubo eruption in the Philippines, the second-largest volcanic eruption of the 20th century, which killed around 800 people.

The Tonga Geological Services agency, which was monitoring the volcano, was unreachable on Monday. Most communications to Tonga have been cut after the main undersea communications cable lost power.

LIGHTNING STRIKES

American meteorologist, Chris Vagasky, studied lightning around the volcano and found it increasing to about 30,000 strikes in the days leading up to the eruption. On the day of the eruption, he detected 400,000 lightning events in just three hours, which comes down to 100 lightning events per second.

That compared with 8,000 strikes per hour during the Anak Krakatau eruption in 2018, caused part of the crater to collapse into the Sunda Strait and send a tsunami crashing into western Java, which killed hundreds of people.

Cas said it is difficult to predict follow-up activity and that the volcano’s vents could continue to release gases and other material for weeks or months.

“It wouldn’t be unusual to get a few more eruptions, though maybe not as big as Saturday,” he said. “Once the volcano is de-gassed, it will settle down.”

 

(Reporting by Kanupriya Kapoor; Editing by Jane Wardell and Michael Perry)

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