On Earth-like planets, the characteristic reflectance spectrum of terrestrial vegetation, known as “vegetation red edge,” is considered as a key biosignature. However, ocean planets, with most of their surfaces covered by water, are unlikely to support terrestrial vegetation. To broaden the scope of life detection on ocean planets, this study examined the characteristics of reflectance spectra from floating plants and tested their detectability.

The study investigated the reflectance spectra of floating plants across different scales, from individual leaves in laboratory settings to large-scale observation via satellite remote sensing of lake vegetation.

Although floating leaves exhibit considerable morphological variation among species, their general trend reveals a pronounced red edge, often comparable to or even exceeding that of terrestrial plants. This enhancement is attributed to air gaps in sponge tissue that provide buoyancy and specialized epidermal structures that offer water repellency. While floating leaves show slightly reduced reflectance when wet, they still display a more distinct red edge than submerged water plants.

However, on a larger scale, the red edge signature of floating vegetation weakens due to lower vegetation density and reduced leaf overlap on the water surface. Landscape-scale analyses using satellite remote sensing (Sentinel-2; ESA) with the Normalized Difference Vegetation Index (NDVI) flourishes in summer and disappears in winter, causing the NDVI to be relatively low when averaged over the year. Nevertheless, the fluctuation between minimum and maximum NDVI values is more pronounced for floating vegetation compared to forests. To further investigate this pattern, a large-scale survey of 148 lakes and marshes across Japan was conducted. The study revealed a characteristic seasonal NDVI variation, shifting from negative values in winter to positive values in summer. Importantly, while water suppresses the reflectance of floating vegetation, its own reflectance is even lower and remains stable. It enhances the detectability of seasonal NDVI fluctuations, which remain robust against atmospheric and cloud interference, suggesting that this method could be promising for detecting life on habitable exoplanets in the future.

If photosynthetic organisms, such as floating plants, exist universally on habitable exoplanets, then the scope of life exploration can be expanded to include ocean planets rather than being limited to Earth-like planets. It is important to understand the origin and evolutionary process of life as it coevolves with planetary environments to predict the morphology of organisms that may adapt to diverse planetary conditions. This study provides a foundation for future research on biosignatures, paving the way for the next generation of life-detection missions.

These populations in south-western Sydney are among the very few in New South Wales (NSW) still free of chlamydia, a highly contagious disease causing infertility that has severely diminished populations elsewhere in the continent’s eastern states.

However, analysis of these koalas led by Dr Elspeth McLennan and Professor Carolyn Hogg at the University’s School of Environmental and Life Sciences shows how vulnerable they are to environmental threats and outbreaks of disease. Highly inbred and with low genetic diversity, they are less likely to adapt to the disease should it arrive on their doorstep.

The findings have been published in Conservation Genetics.

Tissue samples from 111 koalas were collected by NSW Government staff from seven sites in the south-western Sydney suburbs of Liverpool, Campbelltown, Heathcote and Wollondilly, and from Wingecarribee in the Southern Highlands.

Genetic analysis showed a high level of interrelatedness, inbreeding and worryingly low genetic diversity across Sydney koalas.

Low genetic diversity means populations cannot always adapt to change, making them highly susceptible to environmental threats and disease outbreaks.

“On average, koalas in the Sydney populations have cousin or half-sibling relationships,” said Dr McLennan.

Living in highly urbanised areas limits opportunities for Sydney’s koalas to move around and breed with populations further afield and increase the diversity needed to build resilience. However, there is a chance that koalas from the neighbouring Wollondilly Shire, where chlamydia is present, may find their way to the Sydney populations. Gene flow analysis showed koalas are moving between Wollondilly and Campbelltown, the southern-most chlamydia-free site.

“It’s a classic Catch-22 situation,” said Dr McLennan. “If the Wollondilly koalas breed with those elsewhere in Sydney they could increase genetic diversity. But they may bring chlamydia with them. If the latter happens, individual koalas are unlikely to have enough genetic variation to adapt to the threat.

“Instead of some individuals being able to naturally clear chlamydia without it progressing to blindness and infertility, it is possible all individuals will contract the infection whereby it progresses to the later stages of the disease.”

Dr McLennan says there is no ready solution to addressing the threats, including anthropogenic threats from climate change and ongoing urbanisation, to koalas in south-west Sydney. Simply improving habitat connectivity to increase genetic diversity may promote chlamydia spread, she said.

“Beyond south-west Sydney, the results show the importance of managing koala populations and their surrounding landscapes. We need to ensure ongoing connectivity between all koala populations to maintain their health and resilience to threats.”

Koalas in Queensland, New South Wales and the Australian Capital Territory were listed as endangered in 2022. Their populations have decreased 24 percent in the last 20 years.

The research highlights an issue faced by conservationists worldwide too.

“Without diversity, endangered species risk succumbing to disease outbreaks and environmental threats.”

Sheng Xu, an Assistant Professor at Tohoku University’s Frontier Research Institute for Interdisciplinary Sciences, emphasized the importance of the alloy’s wide operational temperature range. “This alloy is the first of its kind to maintain superelasticity at such an extreme range of temperatures while remaining lightweight and strong, which opens up a variety of practical applications that were not possible before. The alloy’s properties make it ideal for future space missions, such as creating superelastic tires for lunar rovers to navigate the extreme temperature fluctuations on the Moon’s surface.”

The alloy’s flexibility at extremely low temperatures makes it a promising material for applications in the forthcoming Hydrogen Society and various other industries. Of course, the alloy can be used in everyday applications requiring flexibility, such as medical devices like stents.

Currently, most shape-memory alloys — materials capable of regaining their original shape after force is removed — are limited to specific temperature ranges. The new Ti-Al-based alloy overcomes this limitation, offering wide applicability in fields that require materials with exceptional strength and flexibility, from space exploration to everyday medical tools.

The research team employed advanced techniques such as rational alloy design and precise microstructure control. By using phase diagrams, the researchers were able to select alloy components and their proportions. Additionally, they optimized processing and heat treatment methods to achieve the desired material properties.

The implications of this study extend beyond immediate practical applications. “This discovery not only sets a new standard for superelastic materials but also introduces new principles for material design, which will undoubtedly inspire further breakthroughs in materials science,” Xu added.

Details of the breakthrough were published in the journal Nature on February 26, 2025.