ASU study: Jupiter’s moon Europa may have had a slow evolution

June 16, 2023

Jupiter's moon, Europa, is slightly smaller than Earth’s moon and is one of the most promising places to search for alien life. 

Amid the Jovian system, Europa is of particular interest to scientists because of the strong evidence for nutrients, water and energy to potentially provide a habitable environment for some form of life beyond Earth. In addition, Europa is believed to be made of four layers (from surface to center): an ice shell, salt water ocean, rocky mantle and metallic core. Illustration of inside Europa. Internal evolution of Europa. Graphic courtesy Kevin Trinh/ASU Download Full Image

Like Earth, Europa’s ocean touches the rocky seafloor, which may allow for rock-water chemistry favorable for life. Some scientists also believe that the seafloor may host volcanoes, which can provide more energy and nutrients for a potential biosphere.

Arizona State University scientists Kevin Trinh, Carver Bierson and Joe O’Rourke of the School of Earth and Space Exploration investigated the consequences of Europa forming with low initial temperatures, using computer code that Trinh wrote. Their findings have been recently published in Science Advances

Hydrated rocks: A key ingredient?

Europa may have a metamorphic origin for its ocean. While some scientists speculated this, Trinh and his team show that if Europa indeed formed from hydrated rocks (i.e., rocks that have hydrogen and oxygen), then enough of Europa’s interior would have gotten hot enough to release water directly from the hydrated rocks to form the ocean and ice shell.

“The origin of Europa’s ocean is important because the moon’s potential to support life ultimately depends on the chemical ingredients and physical conditions during the ocean formation process,” said Kevin Trinh, graduate associate at ASU’s School of Earth and Space Exploration. 

Hydrothermal activity to determine habitability 

Many scientists studying this icy moon assumed that Europa formed with a metallic core during or shortly after accretion. This ASU study contradicts that prediction, instead arguing that Europa may not have started forming its metallic core until billions of years after accretion (if it happened at all).

“For most worlds in the solar system we tend to think of their internal structure as being set shortly after they finish forming. This work is very exciting because it reframes Europa as a world whose interior has been slowly evolving over its whole lifetime. This opens doors for future research to understand how these changes might be observed in the Europa we see today,” said Carver Bierson, postdoctoral research scholar at ASU’s School of Earth and Space Exploration. 

The existence of a metallic core is deeply tied to Europa’s internal heat, which may also be used to drive seafloor volcanism and contribute to a habitable seafloor environment. However, it is unclear whether Europa generated enough heat to form such a core. Trinh’s code calculates how heat is generated and distributed throughout a moon, which uses the same governing equations that many geodynamicists used for decades. The team’s novel result, however, comes from challenging the assumptions common to Europa modeling: A small moon like Europa could form as a cold mixture of ice, rock and metal.

However, all of these processes require a hot interior. A small moon like Europa (approximately 1% of Earth’s mass) may not have enough energy to trigger or sustain Earth-like processes — metallic core formation, seafloor volcanism and ongoing rock-water geochemistry — which implies that Europa’s habitable potential is uncertain. The exact time at which Europa formed determines how much heat is available from the radioactive decay of a short-lived isotope of aluminum. Tidal heating (from gravitational interactions with Jupiter and other moons) also governs how quickly Europa’s interior separates into distinct layers.

In summary, Europa’s seafloor may be cool and hydrated, and may experience limited, if any, seafloor volcanism.

This study implies that there may be limited hydrothermal activity and seafloor volcanism at Europa, which may hinder habitability. However, confident predictions require more data.

“Europa is not just a wet, baby Earth. It is its own special world, full of mysteries to unravel,” said Joseph O’Rourke, assistant professor at ASU’s School of Earth and Space Exploration.

In October 2024, NASA plans to launch a spacecraft called Europa Clipper, which should arrive at Europa in April 2030. With the recent work by Trinh, Bierson and O’Rourke, scientists will be better equipped to interpret incoming data from Europa Clipper, whose main objective is to evaluate Jupiter’s icy moon Europa for the potential conditions to host life.

Media Relations and Marketing Manager, School of Earth and Space Exploration


ASU research team develops breakthrough ultrashort laser pulse technology

Graphene-based lasers could transform communication, solar power and health care

June 16, 2023

From communication and entertainment to manufacturing and health care, lasers have revolutionized the way we interact with the world around us. They have become an integral part of our modern existence, pushing the boundaries of innovation as indispensable components of countless devices and industries.

Lasers produce narrow beams of light. When the laser’s light interacts with the surface of a material on a nanoscale, it emits a wave of light known as a plasmon, and the attributes of a given plasmon can signal information. In optic transmission, a laser pumps light at a component called a saturable absorber to generate an optical signal. Illustration of a laser moving through a 3D square object. Yu Yao, an associate professor of electrical engineering, has developed a method to detect optimal target locations for lasers to improve time and energy usage by several orders of magnitude. Graphic by Erika Gronek/ASU Download Full Image

Yu Yao is an associate professor of electrical engineering in the School of Electrical, Computer and Energy Engineering, part of the Ira A. Fulton Schools of Engineering at Arizona State University. She and her research team at the ASU Center for Photonics Innovation designed a faster and more energy-efficient nanoscale laser component called the graphene-plasmonic hybrid metastructure saturable absorber, known as GPSMA.

GPSMA has potential applications across communication, information processing, spectroscopy and biomedical industries. The absorber can be used to enhance the speed, efficiency and overall performance to advance data transmission, information processing, biomedical sensing and imaging technologies.

Yao’s team has been incorporating an artificially engineered metal-graphene hybrid material in their work due to its beneficial traits in optical modulation and saturable absorption.

In a recent publication in the scientific journal ACS Nano, Yao details her lab’s integration of graphene-based saturable absorbers and how they managed to refine the device to reduce power consumption while maintaining ultrafast response times.

They achieved these significant results by designing an optic antenna array that focuses light into the nanoscale gaps of the material, known as hot spots, to boost absorption. By focusing the laser on these hot spots, they observed improved performance and decreased energy usage.

“Graphene is lightweight and has a fast optical response time but has a low absorption rate in monolayer form,” Yao said. “We designed this device so that light absorption in the nanoscale hot spot can be increased by over three orders of magnitude, resulting in not only strong light absorption but also saturable absorption effects. With GPSMA, we are making a saturable absorber device that could actually reduce power consumption by almost two or three orders of magnitude.”

Their new technique is opening opportunities for infrared laser spectroscopy and high-speed optical signal communication with both fiber-optic cables and satellite communication due to its speed.

“Our device can operate at record-high speed,” Yao said. “Conventional saturable absorbers can operate at nanosecond time scales, but now we’re getting to approximately 60 femtoseconds, which is over 100,000 times faster.”

GPSMA is currently operated at near-infrared wavelength on the electromagnetic spectrum. Thanks to the broad optical response of graphene, it is possible to extend its spectral coverage to longer wavelengths in the infrared spectral region, which are of great interest for molecular spectroscopy and optical communications. Yet, for the longer wavelengths, it is conventionally more difficult to achieve saturable absorbers and generate ultrashort laser pulses. The GPSMA design concept could fill this technological gap.

Yao’s device has potential applications across telecommunications, energy and biomedical industries. The absorber can be used to enhance the speed, efficiency and overall performance of fiber-optic cables, opening opportunities to advance data transmission, solar cell performance and imaging technologies for disease detection.

Hannah Weisman

Science writer, Ira A. Fulton Schools of Engineering, Marketing and Communications