Category: 7. Science

A unique new material that shrinks when it is heated and expands when it is cooled could help enable the ultra-stable space telescopes that future NASA missions require to search for habitable worlds.

One of the goals of NASA’s Astrophysics Division is to determine whether we are alone in the universe. NASA’s astrophysics missions seek to answer this question by identifying planets beyond our solar system (exoplanets) that could support life. Over the last two decades, scientists have developed ways to detect atmospheres on exoplanets by closely observing stars through advanced telescopes. As light passes through a planet’s atmosphere or is reflected or emitted from a planet’s surface, telescopes can measure the intensity and spectra (i.e., “color”) of the light, and can detect various shifts in the light caused by gases in the planetary atmosphere. By analyzing these patterns, scientists can determine the types of gasses in the exoplanet’s atmosphere.

Decoding these shifts is no easy task because the exoplanets appear very near their host stars when we observe them, and the starlight is one billion times brighter than the light from an Earth-size exoplanet. To successfully detect habitable exoplanets, NASA’s future Habitable Worlds Observatory will need a contrast ratio of one to one billion (1:1,000,000,000).

Achieving this extreme contrast ratio will require a telescope that is 1,000 times more stable than state-of-the-art space-based observatories like NASA’s James Webb Space Telescope and its forthcoming Nancy Grace Roman Space Telescope. New sensors, system architectures, and materials must be integrated and work in concert for future mission success. A team from the company ALLVAR is collaborating with NASA’s Marshall Space Flight Center and NASA’s Jet Propulsion Laboratory to demonstrate how integration of a new material with unique negative thermal expansion characteristics can help enable ultra-stable telescope structures.

Material stability has always been a limiting factor for observing celestial phenomena. For decades, scientists and engineers have been working to overcome challenges such as micro-creep, thermal expansion, and moisture expansion that detrimentally affect telescope stability. The materials currently used for telescope mirrors and struts have drastically improved the dimensional stability of the great observatories like Webb and Roman, but as indicated in the Decadal Survey on Astronomy and Astrophysics 2020 developed by the National Academies of Sciences, Engineering, and Medicine, they still fall short of the 10 picometer level stability over several hours that will be required for the Habitable Worlds Observatory. For perspective, 10 picometers is roughly 1/10^th the diameter of an atom.

_{NASA’s Nancy Grace Roman Space Telescope sits atop the support structure and instrument payloads. The long black struts holding the telescope’s secondary mirror will contribute roughly 30% of the wave front error while the larger support structure underneath the primary mirror will contribute another 30%.}

_{Credit: NASA/Chris Gunn}

Funding from NASA and other sources has enabled this material to transition from the laboratory to the commercial scale. ALLVAR received NASA Small Business Innovative Research (SBIR) funding to scale and integrate a new alloy material into telescope structure demonstrations for potential use on future NASA missions like the Habitable Worlds Observatory. This alloy shrinks when heated and expands when cooled—a property known as negative thermal expansion (NTE). For example, ALLVAR Alloy 30 exhibits a -30 ppm/°C coefficient of thermal expansion (CTE) at room temperature. This means that a 1-meter long piece of this NTE alloy will shrink 0.003 mm for every 1 °C increase in temperature. For comparison, aluminum expands at +23 ppm/°C.

_{While other materials expand while heated and contract when cooled, ALLVAR Alloy 30 exhibits a negative thermal expansion, which can compensate for the thermal expansion mismatch of other materials. The thermal strain versus temperature is shown for 6061 Aluminum, A286 Stainless Steel, Titanium 6Al-4V, Invar 36, and ALLVAR Alloy 30.}

Because it shrinks when other materials expand, ALLVAR Alloy 30 can be used to strategically compensate for the expansion and contraction of other materials. The alloy’s unique NTE property and lack of moisture expansion could enable optic designers to address the stability needs of future telescope structures. Calculations have indicated that integrating ALLVAR Alloy 30 into certain telescope designs could improve thermal stability up to 200 times compared to only using traditional materials like aluminum, titanium, Carbon Fiber Reinforced Polymers (CFRPs), and the nickel–iron alloy, Invar.

To demonstrate that negative thermal expansion alloys can enable ultra-stable structures, the ALLVAR team developed a hexapod structure to separate two mirrors made of a commercially available glass ceramic material with ultra-low thermal expansion properties. Invar was bonded to the mirrors and flexures made of Ti6Al4V—a titanium alloy commonly used in aerospace applications—were attached to the Invar. To compensate for the positive CTEs of the Invar and Ti6Al4V components, an NTE ALLVAR Alloy 30 tube was used between the Ti6Al4V flexures to create the struts separating the two mirrors. The natural positive thermal expansion of the Invar and Ti6Al4V components is offset by the negative thermal expansion of the NTE alloy struts, resulting in a structure with an effective zero thermal expansion.

The stability of the structure was evaluated at the University of Florida Institute for High Energy Physics and Astrophysics. The hexapod structure exhibited stability well below the 100 pm/√Hz target and achieved 11 pm/√Hz. This first iteration is close to the 10 pm stability required for the future Habitable Worlds Observatory. A paper and presentation made at the August 2021 Society of Photo-Optical Instrumentation Engineers conference provides details about this analysis.

Furthermore, a series of tests run by NASA Marshall showed that the ultra-stable struts were able to achieve a near-zero thermal expansion that matched the mirrors in the above analysis. This result translates into less than a 5 nm root mean square (rms) change in the mirror’s shape across a 28K temperature change.

Beyond ultra-stable structures, the NTE alloy technology has enabled enhanced passive thermal switch performance and has been used to remove the detrimental effects of temperature changes on bolted joints and infrared optics. These applications could impact technologies used in other NASA missions. For example, these new alloys have been integrated into the cryogenic sub-assembly of Roman’s coronagraph technology demonstration. The addition of NTE washers enabled the use of pyrolytic graphite thermal straps for more efficient heat transfer. ALLVAR Alloy 30 is also being used in a high-performance passive thermal switch incorporated into the UC Berkeley Space Science Laboratory’s Lunar Surface Electromagnetics Experiment-Night (LuSEE Night) project aboard Firefly Aerospace’s Blue Ghost Mission 2, which will be delivered to the Moon through NASA’s CLPS (Commercial Lunar Payload Services) initiative. The NTE alloys enabled smaller thermal switch size and greater on-off heat conduction ratios for LuSEE Night.

Through another recent NASA SBIR effort, the ALLVAR team worked with NASA’s Jet Propulsion Laboratory to develop detailed datasets of ALLVAR Alloy 30 material properties. These large datasets include statistically significant material properties such as strength, elastic modulus, fatigue, and thermal conductivity. The team also collected information about less common properties like micro-creep and micro-yield. With these properties characterized, ALLVAR Alloy 30 has cleared a major hurdle towards space-material qualification.

As a spinoff of this NASA-funded work, the team is developing a new alloy with tunable thermal expansion properties that can match other materials or even achieve zero CTE. Thermal expansion mismatch causes dimensional stability and force-load issues that can impact fields such as nuclear engineering, quantum computing, aerospace and defense, optics, fundamental physics, and medical imaging. The potential uses for this new material will likely extend far beyond astronomy. For example, ALLVAR developed washers and spacers, are now commercially available to maintain consistent preloads across extreme temperature ranges in both space and terrestrial environments. These washers and spacers excel at counteracting the thermal expansion and contraction of other materials, ensuring stability for demanding applications.

For additional details, see the entry for this project on NASA TechPort.

Project Lead: Dr. James A. Monroe, ALLVAR

The following NASA organizations sponsored this effort: NASA Astrophysics Division, NASA SBIR Program funded by the Space Technology Mission Directorate (STMD).

We often think of time—like the 24-hour day—as something fixed and unchanging. But in reality, even Earth’s rotation isn’t constant. Scientists have now found that our planet is spinning faster than it used to, and that means days are getting just a tiny bit shorter.This might sound strange, but Earth’s rotation has always changed over long periods. Dinosaurs, for example, lived with 23-hour days. And in the Bronze Age, the average day was already about half a second shorter than today’s standard. Looking ahead, scientists predict that 200 million years from now, one Earth day will last about 25 hours.

Why is the Earth spinning faster?

Normally, a day lasts 24 hours, or 86,400 seconds. But that’s not completely accurate. Many things—like earthquakes, volcanic activity, ocean tides, and even underground changes—can make the planet spin slightly faster or slower. Even though the overall trend has been for Earth to slow down, something unusual has been happening since 2020.

According to the International Earth Rotation and Reference Systems Service (IERS), based in Washington D.C., the Earth’s rotation has started to speed up. This has been happening steadily enough that experts now believe we may need to remove a leap second from our clocks in 2029—the first time this has ever happened.A recent report from timeanddate.com says that this trend will continue into 2025. Based on current data, the three shortest days of the year will be July 9, July 22, and August 5. The shortest of all, August 5, is expected to be about 1.51 milliseconds shorter than the usual 24 hours.

What’s causing it?

This unexpected speed-up has puzzled experts. Leonid Zotov, a rotation researcher at Moscow State University, told timeanddate.com, “Nobody expected this.” Zotov helped write a 2022 study trying to figure out the cause, but he says that so far, no model fully explains it.

Most scientists believe the answer lies deep inside the Earth—possibly something happening in the core. Ocean and atmosphere changes don’t seem to account for the speed increase.While this spinning trend might continue for now, it’s not a sign that we’re heading back to dinosaur-era days. Earth’s long-term natural tendency is still to slow down over time. Things like melting ice at the poles and surface changes can also affect this.So, while we might “lose” a leap second soon, Earth isn’t going off track—just reminding us that even time isn’t perfectly steady.

The National Institutes of Health (NIH), in collaboration with the U.S. National Science Foundation (NSF), is supporting research to bolster the collection of time-sensitive health data in the wake of Hurricanes Helene and Beryl, the Los Angeles wildfires, and other natural disasters.

The research projects are part of a larger effort by two NIH-NSF-supported research centers to understand how extreme weather affects human health, creates complex exposures to environmental hazards, and impacts access to health care and other vital services.

“This collaborative effort helps fill a long-standing gap by initiating timely health studies and capturing critical health data that may otherwise be lost,” said Aubrey Miller, M.D., Senior Medical Advisor and Director of the NIH Disaster Research Response Program.

He added that disaster research has historically focused on the effectiveness of emergency responses rather than the immediate and long-term health consequences of disasters on our communities.

Supporting quick-response research

The Natural Hazards Center (NHC) at the University of Colorado Boulder is one of two centers working with researchers across the U.S. on this effort. The NHC has supported rapid disaster response research on socio-behavioral impacts through its Quick Response Research Award Program for 40 years. However, the NIH-NSF partnership has provided funding to enable the center to support projects focused on the different health outcomes of these events.

“These awards are transformative,” said Lori Peek, Ph.D., director of the NHC. “We can now explore new frontiers in health and disaster research that have the potential to improve disaster response and future preparedness in immediate and life-saving ways.”

Through this effort, the NHC has provided more than $450,000 in awards to support 12 novel time-sensitive studies following disaster events between 2023 and 2025. A sample of the research projects, and the universities conducting them, follows.

• Assessing community impacts and early warnings in Nebraska tornadoes University of Nebraska Medical Center
• California wildfire smoke events: life course risk perceptions and mental health impacts
  New York University
• Impacts of flooding on opioid use disorder in western Pennsylvania
  The Pennsylvania State University
• Longitudinal evaluation of wildfire impacts on a cohort of people experiencing homelessness in Los Angeles
  University of California, Los Angeles (UCLA)/University of Southern California
• Mental health of community volunteers in the aftermath of Hurricane Helene
  Appalachian State University
• Transit riders’ health risks during the Los Angeles wildfires
  UCLA/University of North Carolina at Chapel Hill/Texas A&M University/California Polytechnic State University/University of Washington/Utah State University

Learn more about all projects funded under the NHC’s special call for health outcomes and disaster research by visiting this website.

Supporting rapid-research technology to understand exposures

The NIH-NSF partnership is also providing funding to the Natural Hazards Reconnaissance (RAPID) Facility at the University of Washington to enable health researchers across the U.S. to have timely access, training, and support to critical instruments for collecting information on exposures. The RAPID Facility provides researchers with uncrewed aircraft systems or drones, hyperspectral and multispectral cameras, and street view imaging to help researchers capture time-sensitive health data in response to wildfires, hurricanes, floods, and other disasters.

The RAPID Facility recently played a critical role in supporting researchers studying the health effects of the Los Angeles wildfires. By providing cutting-edge technology, the RAPID Facility supported immediate, post-fire analysis to improve understanding of wildfire behavior and human exposures. The data collected could be used to conduct long-term health studies and robust environmental exposure assessments.

The first step toward quantum gravity, the “holy grail of physics,” may be hiding in a quantum recipe to cook up black holes.

That’s the suggestion of new research that adds quantum corrections to Einstein’s 1916 theory of gravity, known as “general relativity.” Black holes are relevant to this because they first theoretically emerged from the solutions to the Einstein field equations that underpin general relativity.

Here’s what you’ll learn when you read this story:

• Meteorites found in the Sahara Desert might be pieces of Mercury that broke off as the result of a collision when the Solar System was still forming.

• The meteorites had many parallels to the surface of Mercury, but also some noticeable differences, including a mineral not previously detected on Mercury’s surface.

• Whether or not these rocks are from Mercury remains a mystery, but if not, they could still be useful analogs for understanding more about the innermost planet.

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Though human boots have never set foot on another planet, pieces of Mars have fallen to Earth as meteorites, giving us our only chance to study them up close until NASA’s Mars Sample Return Mission drops off the rock cores collected by Perseverance. Meteorites that emerged from the Sahara desert might be from another resident of our solar system, Mercury.

To say Mercury is extreme is an understatement— it’s hot enough to melt lead, after all. The innermost planet of the solar system is only about 58 million km. (36 million miles) from the Sun, with an average temperature of 167°C (333°F). Few spacecraft have been able to venture anywhere near this scorching clump of iron and silicates without overheating and breaking down. Mariner10 performed the first flyby of Mercury, MESSENGER orbited, and BepiColombo is on its way, but nothing has ever been able to crawl on its surface.

If fragments of Mars could have hurtled to Earth after some ancient collision, then why are there none from Mercury? This is the question planetary scientist Ben Rider-Stokes of The Open University in the UK wanted to answer. MESSENGER has been able to collect data about the surface composition of Mercury, but we have yet to figure out how to send something to pick up samples without being blasted by solar radiation. Stokes examined meteorites that had previously been suspected to have come from Mercury and found possible matches.

“The rise in the number of meteorites collected from hot and cold deserts has greatly expanded the range of meteorite compositions and potential parent objects,” Stokes said in a study recently published in Icarus.

Meteorites Ksar Ghilane 022, which landed in Tunisia, and Northwest Africa 15915, discovered in Morocco, show a surface composition and mineralogy similar to the Mercurian crust. Whether they are actually from Mercury remains unknown. However, both are achondrites, previously melted meteorites characterized by an absence of chondrules (mineral spheres embedded in the rock) and made mostly of silicates such as olivine and pyroxene, often found in igneous and metamorphic rocks. Plagioclase and oldhamite are also present. They also do not fit in with any other known achondrites. There’s just one issue.

What is problematic about both specimens is that the iron-free silicates and oxygen isotopes they contain mirror aubrites, made largely of the translucent silicate mineral enstatite (MgSiO₃). Aubrites have not been detected on the surface of Mercury.

“It is not believed that the aubrites originated from Mercury, as the planet has an extremely red spectrum which differs from aubrite spectra, but it has been suggested that aubrites represent a proto-Mercury,” said Stokes.

Billions of years ago, Mercury might have had a different surface composition before it was pummeled by asteroids, which pockmarked it with craters. Both meteorites are about 4.5 billion years old. This makes them younger than most primitive materials that were swirling around in the solar system, but older than the smooth plains of Mercury, which cover a third of its surface and are around 3.6 billion years old. Even 4-billion-year-old regions of the plains are still no match for the age of the meteorites.

It is possible that the meteorites are actually remnants of Mercury’s crust before there were enough collisions to obliterate that rock and expose the material beneath it. Remnants of this crust on Mercury might have gone undetected, but that knowledge eludes us. BepiColombo is expected to reach Mercury by the beginning of 2026. The spacecraft may be able to find a source of material that is a match for these mysterious rocks.

Even if they aren’t from Mercury, Ksar Ghilane 022 and Northwest Africa 15915 could be analogs for the surface of a planet on which we would’t be able to take the heat.

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