Regents’ Professor John D. Cressler in the School of Electrical and Computer Engineering (ECE) and his students have been working with silicon-germanium heterojunction bipolar transistors (SiGe HBTs) for decades and have found them to have unique advantages in extreme environments like Europa.

“Due to the way that they’re made, these devices actually survive those extreme conditions without any changes made to the underlying technology itself,” said Cressler, who is the project investigator. “You can build it for what you want it to do on Earth, and you then can use it in space.”

The researchers are in year one of a three-year grant in the NASA Concepts for Ocean Worlds Life Detection Technology (COLDTech) program to design the electronics infrastructure for upcoming Europa surface missions. NASA plans to launch the Europa Clipper in 2024, an orbiting spacecraft that will map the oceans of Europa, and then eventually send a landing vehicle, Europa Lander, to drill through the ice and explore its ocean. But it all starts with electronics that can function in Europa’s extreme environment.

Cressler and his students, together with researchers from NASA Jet Propulsion Lab (JPL) and the University of Tennessee (UT), demonstrated the capabilities of SiGe HBTs for this hostile environment in a paper presented at the IEEE Nuclear and Space Radiation Effects Conferencein July.

Europa’s Challenge

Like Earth, Jupiter also has a liquid metal core that generates a magnetic field, producing radiation belts of high-energy protons and electrons from the impinging solar wind. Unfortunately, as a moon of Jupiter, Europa sits squarely in those radiation belts. In effect, any technology designed for Europa’s surface would not only need to be able to survive the cold temperatures but also the worst radiation encountered in the solar system.

Fortunately, SiGe HBTs are ideal for this hostile environment. The SiGe HBT introduces a nanoscale Si-Ge alloy inside a typical bipolar transistor to nano-engineer its properties, effectively producing a much faster transistor while maintaining the economy-of-scale and low cost of traditional silicon transistors. SiGe HBTs have the unique ability to maintain performance under extreme radiation exposure, and their properties naturally improve at colder temperatures. Such a unique combination makes them ideal candidates for Europa exploration.

“It’s not just doing the basic science and proving that SiGe works,” Cressler said. “It’s actually developing electronics for NASA to use on Europa. We know SiGe can survive high levels of radiation. And we know it’s remains functional at cold temperatures. What we did not know is if it could do both at the same time, which is needed for Europa surface missions.”

Testing the Transistors

To answer this question, the GT researchers used JPL’s Dynamitron, a machine that shoots high-flux electrons at very low temperatures to test SiGe in Europa-type environments. They exposed SiGe HBTs to one million Volt electrons to a radiation dose of five million rads of radiation (200-400 rads is lethal to humans), at 300, 200, and 115 Kelvins (-160 Celsius).

“What had never been done was to use electronics like we did in that experiment,” Cressler said. “So, we worked literally for the first year to get the results that are in that paper, which is in essence definitive proof that what we claimed is, in fact, true — that SiGe does survive Europa surface conditions.”

In the next two years, the GT and UT researchers will develop actual circuits from SiGe that could be used on Europa, such as radios and microcontrollers. Yet more importantly, these devices could then be seamlessly used in almost any space environment, including on the moon and Mars.

“If Europa is the worst-case environment in the solar system, and you can build these to work on Europa, then they will work anywhere,” Cressler said. “This research ties together past research that we have done in my team here at Georgia Tech for a long time and shows really interesting and novel applications of these technologies. We pride ourselves on using our research to break new innovative ground and thereby enable novel applications.”

Video: https://youtu.be/hKr6uh4k-7g

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Materials provided by Georgia Institute of Technology. Original written by Tess Malone. Note: Content may be edited for style and length.

Drawn from more than 20 years of observations at Nouabalé-Ndoki National Park in the Republic of Congo, researchers documented social ties between individual chimpanzees and gorillas that persisted over years and across different contexts. The research was conducted by scientists from Washington University, the Wildlife Conservation Society, the University of Johannesburg (South Africa) and Lincoln Park Zoo (Chicago) and is reported in the journal iScience.

“There are few (if any) studies of interactions between primate species that have been able to take the identity of individuals into account,” said Sanz, a professor of biological anthropology in Arts & Sciences. “It has long been known that these apes can recognize individual members of their own species and form long-term relationships, but we had not known that this extended to other species.

“An example of what we found might be one individual traveling through a group of the other species to seek out another particular individual,” she said. “We were also able to document such interactions over time and in different contexts in this study.”

Most people do not realize that the majority of remaining gorillas and chimpanzees reside together.

The large tracts of forest in the Congo Basin are a conservation stronghold not only for these two kinds of endangered great apes but also forest elephants, leopards and many other species. The government of the Republic of Congo and the Wildlife Conservation Society have worked together for nearly three decades to save wild places that sustain the local people, protect natural resources and buffer global climate change.

In a review of published reports combined with a synthesis of previously unpublished data about daily follows of chimpanzees and gorillas from 1999 to 2020 in the Goualougo Triangle, scientists documented ape species engaging in a wide range of social interactions, ranging from play to aggression. Researchers investigated several possible benefits of these interspecies rendezvous, including protection from predation, improved foraging options and other social benefits from information sharing.

What they learned shows us that no ape is an island. “Rather than thinking about chimpanzees alone, we should be thinking about them within diverse and dynamic habitats where they are actively engaging with other species and play an integral role in the persistence of the unique ecosystems in which they exist,” said co-author David Morgan, research fellow at Lincoln Park Zoo.

Why interact at all

One of the key theories that has been suggested for why apes might choose to associate with members of different species is to avoid predators.

But information gathered in this study suggests these social interactions can’t be chalked up to threat reduction. The scientists found little support for the idea that chimpanzees or gorillas are associating to decrease leopard, snake or raptor predation attempts.

“Predation is certainly a threat in this region, as we have cases in which chimpanzees have been killed by leopards,” Sanz said. “However, the number of chimpanzees in daily subgroups remains relatively small, and gorillas within groups venture far from the silverback who is thought to be a protector from predation.”

Instead, enhanced foraging opportunities seem to be more important. The researchers found that co-feeding at the same tree represented 34% of the interspecific associations that they documented, with another 18% of observations involving apes foraging in close spatial proximity but on different foods.

At least 20 different plant species were targeted by apes during co-feeding events in this study, greatly expanding researchers’ knowledge of the diversity of resources that chimpanzees and gorillas are willing to gather together to share.

In addition to a greater diversity of interactions than previously documented among sympatric apes, this study revealed social relationships between members of different species that persisted over years.

For example, study authors noted that on several occasions at food sources, they observed young gorillas and chimpanzees seeking out particular partners to engage in bouts of play. These types of interactions may afford unique development opportunities that extend the individual’s social, physical and cognitive competencies.

“No longer can we assume that an individual ape’s social landscape is entirely occupied by members of their own species,” said co-author Jake Funkhouser, a doctoral candidate of biological anthropology at Washington University. “The strength and persistence of social relationships that we observed between apes indicates a depth of social awareness and myriad social transmission pathways that had not previously been imagined. Such insights are critical given these interspecies social relationships have the potential to serve as transmission pathways for both beneficial socially learned cultural behaviors and harmful infectious disease.”

Concerns about disease transmission

Certainly, social exchanges between apes have their risks. One is the potential for disease transmission. While poaching and habitat loss still represent the largest threats to apes, infectious disease has recently emerged as a threat of similar magnitude.

Because chimpanzees and gorillas are closely related, many pathogens can be transmitted between them. Ebola, for example, is a highly transmissible virus that has had a devastating impact on ape populations in central Africa. Just over 20 years ago, Ebola emerged in wild ape populations and then spread to humans. By some estimates, that wave of the Ebola virus wiped-out one-third of the world’s chimpanzees and gorillas.

“While we continue to be concerned about many disease risks, we now know much more about the origin of many of these pathogens and routes of their transmission within and between species, including humans,” Sanz said.

In this study, “the surprise to us was the extent of overlap and interaction that occurred between these apes that was previously not recognized or reported,” she said. “Based on the literature, we had anticipated that the apes would avoid one another … and in some cases, it seemed to be the opposite.”

Co-existing comfortably

Studying co-existing great apes may inform us about interactions between some early hominins, study authors said.

There has been a long history in paleoanthropology of assuming that early hominins would competitively exclude each other from using the same resources in the same areas. But if modern-day observations with non-human apes are informative about the behavior of early modern humans, then this study suggests these interactions would have most likely occurred in tolerant social contexts.

Sanz emphasizes the continuing importance of longitudinal studies to understand chimpanzee and gorilla behavior and ecology — but also to protect these apes and their habitats.

“Despite more than 60 years of chimpanzee and gorilla research, there is still much to be learned about these fascinating apes — the main challenge at this time is to ensure the conservation of these endangered species so that such opportunities exist for future generations,” she said.

On Sept. 26, 2022, at 7:14 pm EDT, DART intentionally crashed into Dimorphos, the asteroid moonlet in the double-asteroid system of Didymos. It was the world’s first test of the kinetic impact mitigation technique, using a spacecraft to deflect an asteroid that poses no threat to Earth, and modifying the object’s orbit. DART is a test for defending Earth against potential asteroid or comet hazards.

The coordinated Hubble and Webb observations are more than just an operational milestone for each telescope — there are also key science questions relating to the makeup and history of our solar system that researchers can explore when combining the capabilities of these observatories.

“Webb and Hubble show what we’ve always known to be true at NASA: We learn more when we work together,” said NASA Administrator Bill Nelson. “For the first time, Webb and Hubble have simultaneously captured imagery from the same target in the cosmos: an asteroid that was impacted by a spacecraft after a seven-million-mile journey. All of humanity eagerly awaits the discoveries to come from Webb, Hubble, and our ground-based telescopes — about the DART mission and beyond.”

Observations from Webb and Hubble together will allow scientists to gain knowledge about the nature of the surface of Dimorphos, how much material was ejected by the collision, and how fast it was ejected. Additionally, Webb and Hubble captured the impact in different wavelengths of light — Webb in infrared and Hubble in visible. Observing the impact across a wide array of wavelengths will reveal the distribution of particle sizes in the expanding dust cloud, helping to determine whether it threw off lots of big chunks or mostly fine dust. Combining this information, along with ground-based telescope observations, will help scientists to understand how effectively a kinetic impact can modify an asteroid’s orbit.

Webb Captures Impact Site Before and After Collision

Webb took one observation of the impact location before the collision took place, then several observations over the next few hours. Images from Webb’s Near-Infrared Camera (NIRCam) show a tight, compact core, with plumes of material appearing as wisps streaming away from the center of where the impact took place.

Observing the impact with Webb presented the flight operations, planning, and science teams with unique challenges, because of the asteroid’s speed of travel across the sky. As DART approached its target, the teams performed additional work in the weeks leading up to the impact to enable and test a method of tracking asteroids moving over three times faster than the original speed limit set for Webb.

“I have nothing but tremendous admiration for the Webb Mission Operations folks that made this a reality,” said principal investigator Cristina Thomas of Northern Arizona University in Flagstaff, Arizona. “We have been planning these observations for years, then in detail for weeks, and I’m tremendously happy this has come to fruition.”

Scientists also plan to observe the asteroid system in the coming months using Webb’s Mid-Infrared Instrument (MIRI) and Webb’s Near-Infrared Spectrograph (NIRSpec). Spectroscopic data will provide researchers with insight into the asteroid’s chemical composition.

Webb observed the impact over five hours total and captured 10 images. The data was collected as part of Webb’s Cycle 1 Guaranteed Time Observation Program 1245 led by Heidi Hammel of the Association of Universities for Research in Astronomy (AURA).

Hubble Images Show Movement of Ejecta After Impact

Hubble also captured observations of the binary system ahead of the impact, then again 15 minutes after DART hit the surface of Dimorphos. Images from Hubble’s Wide Field Camera 3 show the impact in visible light. Ejecta from the impact appear as rays stretching out from the body of the asteroid. The bolder, fanned-out spike of ejecta to the left of the asteroid is in the general direction from which DART approached.

Some of the rays appear to be curved slightly, but astronomers need to take a closer look to determine what this could mean. In the Hubble images, astronomers estimate that the brightness of the system increased by three times after impact, and saw that brightness hold steady, even eight hours after impact.

Hubble plans to monitor the Didymos-Dimorphos system 10 more times over the next three weeks. These regular, relatively long-term observations as the ejecta cloud expands and fades over time will paint a more complete picture of the cloud’s expansion from the ejection to its disappearance.

“When I saw the data, I was literally speechless, stunned by the amazing detail of the ejecta that Hubble captured,” said Jian-Yang Li of the Planetary Science Institute in Tucson, Arizona, who led the Hubble observations. “I feel lucky to witness this moment and be part of the team that made this happen.”

Hubble captured 45 images in the time immediately before and following DART’s impact with Dimorphos. The Hubble data was collected as part of Cycle 29 General Observers Program 16674.

“This is an unprecedented view of an unprecedented event,” summarized Andy Rivkin, DART investigation team lead of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland.