Astronomy

The arrival of spacecraft on alien worlds uses a number of different techniques from giant air bags to parachutes and small rockets. The use of rockets can pose a problem to onboard technology though as the dust kicked up can effect sensors and cameras and the landing site can be disturbed in the process. A team of researchers have developed a new instrument that can measure the dust that is kicked up on landing to inform future instrument design. 

Dust can have a significant impact on spacecraft during landing especially on bodies like the Moon and Mars. Both worlds have a fine layer of dust on the surface known as the regolith. On descent, landing thrusters can stir up large clouds of dust which reduces visibility having an impact on navigation systems, and reducing visibility. It can damage optical instruments causing scratches on lenses and accumulation of dust on solar panels. Particles can even stick to spacecraft through electrostatic adhesion leading to overheating and mechanical problems. 

After taking the first boot print photo, Aldrin moved closer to the little rock and took this second shot. The dusty, sandy pebbly soil is also known as the lunar ‘regolith’. Click to enlarge. Credit: NASA

There are existing systems and instruments available to analyse the dust cloud but those instruments rely upon visual imaging, x-ray or MRI technology. The research team at the University of Illinois have developed technology that can assess displaced dust clouds using radio waves of 3.8mm wavelength. This enables them to deal with particle clouds too dense for optical examination or too thin for the x-ray analysis. The new instrument sends out radio waves just like a radar, the waves travel through the cloud and a picture of the cloud is built up. 

Illustration of SpaceX Starship landing on Mars. Credit: SpaceX

The new technique relies upon the concept that the waves are generally larger than the dust particles. As they travel through the dust, they are slowed down by a tiny amount and this reduction in velocity enables the cloud to be modelled. If light waves were used, they could not pass through the dust. 

The Radar Interferometry for Landing Ejecta or RIFLE as it has been called began development back in 2020 when radar was identified as the right technology. The original concept employed absorption measurements instead of measurements of the speed of the signal but that had problems. Unfortunately there were problems with this approach; larger clouds would cause a weaker radar signal on measuring absorption, the cloud also caused problems acting like a lens to focus waves onto a receiver and affecting the measurements. The team then turned their attention upon interferometry instead.

The team found the results were far more accurate so worked upon the development of prototypes and a final working instrument. A funnel was used to create a thin curtain of dust of known concentration. They then used cameras with lights to cast shadows of the dust particles at high magnification. The dust concentrations were measured optically to enable the instrument to be calibrated for use. The team have now applied for a patent following the successful test phase. 

Source : New instrument uses radar to measure what the eye can’t see

The post Measuring How Much Dust Spacecraft Kick Up When they Land appeared first on Universe Today.

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The source of Earth’s water is an enduring mystery that extends to exoplanets and the notion of habitability. In broad terms, Earth’s water was either part of the planet from the beginning of its formation in the solar nebula or delivered later, maybe by asteroids and comets.

New research suggests that the Sun’s relentless solar wind could’ve played a role.

Scientists have worked hard to understand how Earth has so much life-giving water. There’s lots of research supporting the asteroid/comet delivery scenario. There’s also evidence that it accumulated water as it grew. During its accretion phase, it may have absorbed water-rich planetesimals.

To try to understand how Earth’s water fits into the history of the planet and the Solar System, researchers examine the isotope ratio on Earth and in meteorites. The isotopic composition of Earth’s water is most similar to primitive meteorites. On the other hand, it’s different from that of comets and nebular gas.

This implies that Earth’s water came from the same cosmochemical reservoir that is also the source of primitive meteorites.

It’s a complicated issue. Maybe Earth’s water has multiple sources. Maybe some of it was created in space long after Earth and the rest of the Solar System formed, and then delivered to Earth.

New research in The Astrophysical Journal explores how water can be created by the solar wind as it strikes surfaces holding oxygen-containing minerals. It’s titled “Stellar Wind Contribution to the Origin of Water on the Surface of Oxygen-containing Minerals.” The lead author is Svatolpuk Civiš from the J. Heyrovský Institute of Physical Chemistry at the Czech Academy of Sciences in Prague.

The solar wind is a steady stream of charged particles—mostly protons and electrons—that come from the Sun. H+ ions, which are simply protons, are the most abundant particles in the solar wind. They make a big contribution to the solar wind’s properties. Could the wind trigger the creation of water molecules?

The researchers performed laboratory experiments to find out. They tested 14 oxygen-containing minerals. “To investigate the process of water formation on the surface of oxidic materials and water abundances, we used the technique of surface bombardment with hydrogen or deuterium atoms and ions,” the authors write in their paper.

The list of materials tested in the laboratory. Note that two of the samples are meteorites and that one of the samples, TiO2 P25 anatase, did not produce water in its discharge. Image Credit: Civiš et al. 2024.

The experiments had two phases: the first tested whether the minerals would produce water when exposed to the solar wind, and the second tested their adsorption capacity. Separate from absorption, adsorption is the adhesion of a sample to a surface.

The team produced water and then measured it using two methods: a microwave (MW) discharge experiment and sputter gun irradiation. They tested the results with a type of spectrometry analysis called Fourier-transform infrared spectrometry (FTIR) and temperature-programmed desorption (TPD) analysis.

“Both these experiments include a mineral sample bombarded by hydrogen/deuterium ions, which, among other possibilities, react with surface oxygens in the mineral lattice and form water molecules,” the authors write.

This figure illustrates the two types of laboratory tests. The left panel shows the MW discharge method and the right panel shows the Ion sputter gun method. Image Credit: Civiš et al. 2024.

The oxide material samples were not only exposed to the strong current of H, H+ and molecular hydrogen that mimic the solar wind. They were also exposed to intense visible and UV radiation generated in the hydrogen discharge.

“The stellar wind irradiation of rocky oxygen-containing minerals results in a reaction between H+ ions and silicate minerals to produce water and OH, which could explain the presence of water in the regoliths of airless worlds such as the Moon, as well as the water abundances in asteroids,” the authors write.

Previous research has established that a chemical reaction occurs between hydrogen ions and silicate minerals when rocky materials are exposed to solar wind irradiation. Some researchers have observed the formation of OH (hydroxide) and water, while others have only found OH. This research goes deeper by testing the rocky materials for water adsorption.

The researchers tested the samples’ water adsorption capacity. Then, they calculated how much material would need to reach Earth to account for the amount of water on contemporary Earth.

“Besides material acquired by the Earth during accretion, the solar wind origin of water and its delivery to Earth could have gone on even during post-accretional bombardment,” the authors write. Here, they’re referring to the hypothetical Late Heavy Bombardment.

Previous research shows that ” asteroid and comet impacts during the classical Late Heavy Bombardment would bring in about ?1020 kg of material,” the authors write. “If that material’s surface was fully saturated with adsorbed water as composed of one of our minerals, our calculations suggest that at least one ocean equivalent of water could have been brought in.”

This schematic from the research shows how the solar wind can create water molecules on rocky bodies like asteroids. The water is adsorbed into a thin film and adheres to the asteroid. Eventually, some of this water is delivered to Earth by impacts. Image Credit: Civiš et al. 2024.

There’s not much doubt about the results of these tests and the ability of the solar wind to create water.

“The results of the experiments summarized in this work, focused on surface bombardment with hydrogen atoms, clearly confirm the theory of the interaction of excited hydrogen or deuterium Rydberg atoms and ions with the surface oxygens of oxide minerals,” the authors explain. “Our experiments attempt to explain the origin of water in the areas of oxygen-containing solid material (e.g., dust, meteoroids, asteroids, comets) exposed to a stream of charged particles close to a parent star.”

Earth’s atmosphere and magnetosphere shield it from the solar wind, so there’s no way the wind could’ve created water right on Earth’s surface. However, as the study shows, the wind can create water on the surface of other bodies like asteroids, and the water can be adsorbed and held firm, then delivered to Earth via impacts.

“This scenario is also applicable to the origin of water on Earth,” the authors write. “Due to this effect, a water molecule can be adsorbed on the surface of oxygen-containing particles and then transported over long distances and times,” the researchers write.

This study won’t be the end of the ongoing effort to account for Earth’s water. In a fascinating roundabout way, this research brings us back to asteroids and meteorites delivering Earth’s water. If it can happen here, it can happen on exoplanets elsewhere in the galaxy.

The post Did Some of Earth’s Water Come from the Solar Wind? appeared first on Universe Today.

A super blue moon rises above NASA's Kennedy Space Center in Florida on Monday, Aug. 18, 2024. Although not actually appearing blue, as the third full moon in a season with four full moons, this is called a “blue” moon.

Sending an object to another star is still the stuff of science fiction. But some concrete missions could get us at least part way there. These “interstellar precursor missions” include a trip to the Solar Gravitational Lens point at 550 AU from the Sun – farther than any artificial object has ever been, including Voyager. To get there, we’ll need plenty of new technologies, and a recent paper presented at the 75th International Astronautical Congress in Milan this month looks at one of those potential technologies – electric propulsion systems, otherwise known as ion drives. 

The paper aimed to assess when any existing ion drive technology could port a large payload on one of several trajectories, including a trip around Jupiter, one visiting Pluto, and even one reaching that fabled Solar Gravitational Lens. To do so, they specified an “ideal” ion drive with characteristics that enabled optimal values for some of the system’s physical characteristics.

First among those characteristics is the power plant. Ion thrusters need a power source and an effective one if they will last more than a decade under thrust. The paper defined an ideal power plan that can output 1 kW per kg of weight. This is currently well outside the realm of possibility, with the best ion thruster power sources coming at something like 10 W per kg and even nuclear electric propulsion systems outputing 100 W per kg. Some potentially better technologies are on the horizon, but nothing tested in the literature would meet this requirement yet.

Fraser discusses the concept of the solar gravitational lens with Dr. Slava Turyshev

Thrust efficiency is another consideration for this idealized mission. The authors, who are writing under the banner of the Initiative for Interstellar Studies, a non-profit group based out of the UK, suggested that an idealized thrust efficiency is 97%. That would also significantly improve existing technologies, which average closer to 75-80% efficiency for working models. Additional improvements could increase this number, such as magnetic containment fields around the thruster’s walls. Still, as it gets closer to that 97% range, finding efficiency improvements becomes harder and harder.

The last characteristic the authors considered was the specific impulse. This one has the most comprehensive variability regarding the theoretical potential of all three systems. Their idealized value of 34,000-76,000 seconds of specific impulse is well within the bounds of the potential values for more speculative technologies. The paper mentions that specific impulse values twice the suggested upper range could be possible with the proper selection of thruster and propellant. They also point out that development on these technologies is stalled not because we can’t make drives with better specific impulse but because we can’t produce power plants that support them yet. So, solving the power plant issue will enable further development in this area.

Fraser discusses the details of ion engines and why they’re so efficient.

Suppose all three characteristics were combined into a complete functional propulsion system. In that case, the authors calculate that it could deliver a payload of almost 18,000 kg to the Solar Gravitational Lens in just 13 years – much faster than any previous mission would be capable of. But that optimization is still a long way off, and while there are missions planned for deployment to the SGL someday, it is still a long way off before they launch and even longer before they arrive there. In the meantime, engineers have some additional problems to solve if they want to optimize the potential of ion thrusters.

Learn More:
N Maraqten, D Fries, A Genovese – Advanced Electric Propulsion Systems with Optimal Specific Impulses for Fast Interstellar Precursor Missions
UT – Next Generation Ion Engines Will Be Extremely Powerful
UT – Ion Engines Could Work on Earth too, to Make Silent, Solid-State Aircraft
UT – The Most Powerful Ion Engine Ever Built Passes the Test

Lead Image:
Ion Thruster
Credit – NASA

The post Ion Engines Could Take Us to the Solar Gravitational Lens in Less Than 13 Years appeared first on Universe Today.

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