Tag Archives: surface

Covid-19 survival time on surfaces depends on the material

While past research has determined that SARS-CoV-2 can survive for several days on surfaces and in aerosol form, a new study reports that reality is a bit more complicated than that.

Carton, Ondulat, Hârtie, Structura, Fondul, Filmate
Image via Pixabay.

While the virus is still detectable on contaminated objects and surfaces (for up to three hours in aerosols, up to four hours on copper, up to 24 hours on cardboard and up to two to three days on plastic and stainless steel).

SARS-CoV-2 is quite infectious even through casual physical contact, making it very hard to contain. The study aimed to investigate the risk presented by coronavirus spread unknowingly by people in their daily lives — the risk of contracting the virus from particles deposited on surfaces through coughing, for example. According to the findings, the virus can survive for up to three hours in aerosols, up to four hours on copper, up to 24 hours on cardboard, and up to two to three days on plastic and stainless steel.

The time of my life

“This virus is quite transmissible through relatively casual contact, making this pathogen very hard to contain,” said James Lloyd-Smith, a co-author of the study and a UCLA professor of ecology and evolutionary biology.

“If you’re touching items that someone else has recently handled, be aware they could be contaminated and wash your hands.”

The researchers tried to mimic the way this virus is being deposited onto usual surfaces in households and hospitals by asking an infected person to cough on or touch various objects. Then, they measured how long the virus remained alive on these surfaces.

Plastic and stainless steel were pretty cozy environments for the virus, the team explains, much more so than copper and cardboard. However, the total population numbers dramatically reduced on plastic and steel, after 72 and 48 hours respectively. The findings do go a long way toward tempering fears; in essence, this study found that while past research did reach a fair assessment of the virus’ longevity on different surfaces, its ability to infect us falls sharply over that timeframe and that the rate at which virus populations shrink is linked to the material they live on.

So while getting packages in the mail should be pretty safe, the team wants to make sure that everyone is doing their best to avoid the virus. Their findings, they explain, support common public health guidance measures:

  • Avoid close contact with people who are sick.
  • Avoid touching your eyes, nose, and mouth.
  • Isolate yourself at home when you are sick.
  • Cover coughs or sneezes with a tissue, and dispose of the tissue in the trash.
  • Clean and disinfect frequently touched objects and surfaces using a household cleaning spray or wipe.

The paper “Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1” has been published in the New England Journal of Medicine.

European satellites track climate shifts using ocean salinity

New research from the European Space Agency (ESA) Climate Change Initiative is offering new insight into sea-surface salinity across the world. The data will help researchers better estimate the effects of climatic shifts on the world’s oceans.

Global sea-surface salinity maps from ESA’s Climate Change Initiative.
Image credits European Space Agency.

Ocean water is salty — but these salt levels aren’t the same everywhere. This saltiness is a key variable in the Earth’s climate systems, as it’s the product of multiple different factors (additions of freshwater from rivers, rain, glaciers or ice sheets, or on the removal of water by evaporation). Understanding how salinity changes over time and distance can help us better understand (and predict) man-made climate change. Now, thanks to the ESA’s efforts, we can monitor it from space.


“The project aims to make a significant improvement to the quality and length of the datasets available for monitoring sea-surface salinity across the globe,” says Susanne Mecklenburg, head of ESA’s Climate Office.

“We are keen to see this new dataset used and tested in a variety of applications, particularly to improve our understanding of the fundamental role that oceans have in climate.”

The ongoing project from the ESA’s Climate Change Initiative (CCI) has produced the most complete dataset of sea-surface salinity around the world to date. The CCI aims to generate accurate and long-term datasets pertaining to 21 Essential Climate Variables set out under the United Nations Framework Convention on Climate Change and the Intergovernmental Panel on Climate Change.

Sea-surface salinity maps can be used to monitor natural water cycles, evaporation rates, and ocean circulation. These processes are central elements of the climate system of today as they help transport heat, nutrients and carbon around the planet. Unusual salinity levels can also indicate that extreme climate events, such as El Niño, are about to start.

Such measurements have been taken before — they indicate that ever since the 1950s, salty areas around the world are becoming saltier, while freshwater areas are becoming fresher. However, there has always been a measure of debate over these findings, as they relied on scientific ships trawling the oceans to read salinity, which provides relatively poor accuracy (as they’re quite slow to move around). Using satellites to capture a global snapshot would give us a much better idea of what’s happening.

The team behind the project, Jacqueline Boutin of LOCEAN (Laboratory of Oceanography and Climatology) and Nicolas Reul of IFREMER (French Research Institute for the Exploitation of the Sea) pooled together data from three satellite missions to create a dataset spanning nine years, with maps generated on a weekly and monthly basis.

The team measured brightness temperature as a proxy for sea-surface salinity using microwave sensors onboard the SMOS, Aquarius, and Soil Moisture Active Passive satellite missions.

“Monitoring salinity from space helps to resolve spatial and temporal scales that are poorly sampled by in situ platforms that make direct observations, and fills gaps in the observing system,” says Dr. Boutin.

“By combining and comparing measurements between the different sensors, [we improved] the precision of maps of sea-surface salinity by roughly 30%.”

Ocean–atmosphere exchanges around the world are driven by winds and exchanges between surface and subsurface ocean water, the team explains. These later ones are powered by changes in water density, a product of both temperature and salinity (salty water is denser than freshwater). In the deep ocean, density variations are the main driver for the movement of water. Studying changes in salinity, the team explains, can thus help better model ocean-atmosphere exchanges, and the behavior of deeper ocean layers — both of which will allow us to better estimate climate shifts in the future.

The team is currently working with climate scientists to compare the new dataset with in situ observations and with the output from salinity models.

The dataset is freely available for download from the CCI Open Data Portal.

Prairie stream.

Earth is much more rivery than we’ve suspected, satellite data reveals

There are a lot of rivers on Earth — many more than we’ve assumed.

Prairie stream.

Image credits Alex Hu.

Previous estimations of river- and stream- cover on our planet haven’t exactly been accurate, according to new research from the University of North Carolina. Excluding land covered with glaciers or ice sheets, our planet is braided with about 300,000 square miles (773,000 square kilometers) of rivers and streams — 44% more area than previously estimated.

My river runneth over

To find out just how much ‘river’ you need to make one ‘Earth’, the team — University of North Carolina hydrologists George Allen and Tamlin Pavelsky — drew on thousands of images recorded by NASA’s Landsat satellite. Using software that Pavelsky designed specifically for this task, they took over 58 million measurements of rivers, streams, and other similar waterways. The researchers estimated river shapes by measuring their widths. Finally, they added all of them up to calculate the total surface area they cover.

To make sure that the software wouldn’t foul the measurements, the team recruited “a small army of undergrads” to monitor the program as it went about its task. One of the team’s main concerns was that roads or other similar structures could be treated as rivers by the program, but this turned out not to be the case.

Aside from finding those extra 300,000 square miles of river (roughly the same size of Texas, to put it into perspective), the researchers also report that rivers were both narrower and more sparse in developed areas. This could come down to seasonal variations, water drainage for agriculture, habitat removal (such as drainage of swamps), or the corraling of rivers for hydroelectricity. The team can’t say for sure what the cause is, however, and call for further research into the area.

Not only will the findings send fishing enthusiasts cheering for their rods, it also has some more worrying implications. Namely, it influences how we study and deal with climate change. Waterways are a prime source of greenhouse gas exchange between the surface and the atmosphere, especially when waters are polluted.

For a very long time, people were content to let rivers soak up pollutants completely secure in the belief that these compounds will wind up in the ocean. It was a simpler time when we thought we could afford this. Over the past decade, however, researchers have wisened up to the fact that rivers instead help break down this waste, and release greenhouse gasses into the atmosphere. Some of the most common river-borne pollutants are fertilizers, sewage, and drainage from soils — and the wet, relatively oxygenated, and biodiverse backdrop of a river is an excellent place for these to break down. As they break down, they release gasses such as methane, nitrous oxide, and carbon dioxide into the atmosphere. Even if they do wind up in the ocean, that is by no means a get out of jail card.

If rivers cover up more area than we assumed (and the 44% more this paper reports on is significantly more) then our current calculations regarding how much greenhouse gas they release need to be re-crunched.

“If you look around the world, rivers look different from place to place,” Allen told Gizmodo. “They might be braided, or sinuous, or meandering. And for the most part, current technology doesn’t take into consideration the actual morphology of rivers. This data set is the first of its kind to do this at a global scale on high resolution.”

This global map of rivers might also help predict floods and it will be an invaluable resource in the future, when we’re trying to keep track of how rivers behave as the Earth warms up.

The paper “Global extent of rivers and streams” has been published in the journal Science.

Fishing areas.

In 2016, fishing ships cast their nets on over 55% of the ocean surface

Fishing now extends to over half the ocean surface on Earth, a new study shows — and some areas are surprisingly busy.

Fishing areas.

Each dot represents the average hours of fishing activity within an area of 10,000 square kilometers (3861.022 sq mi).
Image credits A. Kroodsma et al., 2018, Science.

Oceans cover more than two thirds of our planet’s surface, which is why we affectionately call it the Blue Planet. It might be time for us to seriously consider changing that name to the Fishing Planet, as industrial fishing occurred across more than 55% of overall ocean area in 2016, new research has found.

To put that into perspective, only 34% of the planet’s land area was used for agriculture or grazing in 2016.


Previous attempts at tracking and quantifying global fishing activity haven’t been very successful, mostly because of the data they worked with — a mess of data drawn from electronic monitoring systems on some vessels, logbooks, or even onboard observers on others.

Over the last 15 years, however, almost all commercial-size ships have been outfitted with AIS, or automatic identification system, transceivers. These instruments track the ship in real time and are meant to help ships avoid collisions at sea. The team drew on this cache of data for their study. They examined 22 billion AIS positions, recorded between 2012 and 2016. Using machine learning, they identified over 70,000 fishing ships based on these positions and then recorded their activity.

Most fishing, they report, took place in countries’ exclusive economic zones (EEZs), which isn’t that surprising. EEZs are ocean regions roughly within 370 kilometers of a nation’s coastline, within which the UN Convention on the Law of the Sea grants states special rights to explore for and exploit marine resources.

However, there were also hotspots of fishing activity further out in the open ocean, the team adds. Such spots included the Northeastern Atlantic Ocean and the areas of nutrient-rich upwellings off the coasts of South America and West Africa. Just five countries — China, Japan, Taiwan, Spain, and South Korea — accounted for roughly 85% of all fishing outside of any EEZ.

Tracking fishing efforts over space and time can help guide policy on the matter, to make sure fish stocks are harvested in a sustainable manner. The data can also help tailor marine environmental protections and international conservation efforts for fish, which are having a really hard time surviving. In the face of rising sea levels, and an increase in human activity at sea, both of these tasks could become central talking points in geopolitics, and would have a direct impact over consumer quality of life.

The paper “Tracking the global footprint of fisheries” has been published in the journal Science.

Satellite imagery seasons

NASA records 20 years of changing seasons in new global map

A striking new video released by NASA shows how the surface of the planet transforms over 20 years of changing seasons.

Satellite imagery seasons

Credit: NASA/Youtube.

“It’s like watching the Earth breathe. It’s really remarkable*,” said NASA oceanographer, Jeremy Werdell, in a statement.

“It’s like all of my senses are being transported into space, and then you can compress time and rewind it, and just continually watch this kind of visualization,” he added.

Scientists constructed the visualization with data compiled from September 1997 to September 2017. These twenty years have been condensed in two-and-a-half minutes of mesmerizing imagery that shows how Earth’s surface ebbs and flows with the seasons.

In this dance of the seasons, you can witness how Earth’s vegetation changes. By monitoring the color of reflected light via satellite, scientists can determine how successfully plant life is photosynthesizing, which can be highly important when assessing biosphere health.

Polar ice caps and snow cover extends and retreats while oceans transition from shades of blue and green into hues of red and purple as marine life blooms or goes under. The algae bloom of 1997-1998 is particularly striking, having turned sizable areas of the Pacific into a bright green, spurred by a water-warming El Nino merged with a cooling La Nina.


It took three months of hard work to complete the visualization of satellite imagery but in the end, it was all worth it. Now, policymakers, but also businesses like commercial fishermen, can use these resources in their decision-making process.

This is only the beginning. Like the seasons, NASA’s visualization will only change. Engineers will improve their renditions with each new version as more and better remote-sensing satellites making into Earth’s orbit.

Blood, plasma and water droplets beading on a superomniphobic surface. Colorado State University researchers have created a titanium surface that's specifically designed to repel blood. (Credit: Kota Lab / Colorado State University)

Blood-repelling surface might finally put an end to clotting in medical implants

Blood, plasma and water droplets beading on a superomniphobic surface. Colorado State University researchers have created a titanium surface that's specifically designed to repel blood. (Credit: Kota Lab / Colorado State University)

Blood, plasma and water droplets beading on a superomniphobic surface. Colorado State University researchers have created a titanium surface that’s specifically designed to repel blood. (Credit: Kota Lab / Colorado State University)

Medical implant designers have always found it challenging to make their prostheses both biocompatible and safe from blood clotting. The solution might have been found at the interface between material science and biomedical engineering as Colorado State University engineers recently demonstrated. A team there designed a “superhemophobic” titanium surface that’s extremely repellent to blood. Tests ran in the lab suggest that blood would stay clear of an implant coated with this surface averting clots and infection that usually require doctors to perform surgery again.

Arun Kota and Ketul Popat, both from Colorado State University’s mechanical engineering and biomedical engineering departments, combined their expertise in an effort to design a surface that repels blood. Kota is an expert in superomniphobic materials (the kind that can repel virtually any liquid) while Popat’s work has been focused on tissue engineering and bio-compatible materials.

The two had to venture through unexplored terrain, as the typical approach has so far been the opposite. Medical implant engineers usually design “philic” surfaces that attract, not repel, blood so these are more biocompatible.

“What we are doing is the exact opposite,” Kota said. “We are taking a material that blood hates to come in contact with, in order to make it compatible with blood.”

That may sound confusing but the finished piece performed as intended. The researchers started with plain sheets of titanium whose surfaces they chemically altered to create a ‘phobic’ geometry onto which blood can’t come in contact with. It’s akin to how the lotus leaf repels water thanks to its nanoscale texture, only Kota and Popat’s surface was specially designed to repel blood. Experiments suggest very low levels of platelet adhesion, the biological process that eventually can lead to blood clotting and even biological rejection of the foreign material.

What the titanium's chemically altered surface looks like. The 'spikes' repel the blood. Credit: Colorado State Uni.

What the titanium’s chemically altered surface looks like. These ‘spikes’ repel the blood. Credit: Colorado State Uni.

Because the blood is ‘tricked’ that there is no surface blocking its flow, for all intents and purposes there is no foreign material.

“The reason blood clots is because it finds cells in the blood to go to and attach,” Popat said.

“Normally, blood flows in vessels. If we can design materials where blood barely contacts the surface, there is virtually no chance of clotting, which is a coordinated set of events. Here, we’re targeting the prevention of the first set of events.”

Next on the drawing board is to test new textures and chemistries. So far, fluorinated nanotubes seem to offer the best protection against clotting. Other clotting factors will also be examined and hopefully the Colorado State team may soon have the chance to test their work with real medical devices.

The findings were reported in the Advanced Healthcare Materials journal.