Hexbyte Glen Cove Perseverance dumps contents of Sample Tube 261 in first step to clear rocky anomaly

Hexbyte Glen Cove

NASA’s Mars Perseverance rover acquired this image using its onboard SHERLOC WATSON imager. The camera is located on the turret at the end of the rover’s robotic arm. The image was acquired on Jan. 13, 2022 (Sol 320). Credit: NASA/JPL-Caltech

NASA’s Mars 2020 mission team has been working methodically and thoroughly, making good progress on understanding the best path forward to remove the uninvited pebbles from Perseverance’s bit carousel. Over the previous weekend, and earlier this week, operational sequences were developed and tested to remove these rocky interlopers.

With terrestrial experimentation complete, we have begun executing our mitigation strategy on Mars. On Jan. 12 we did a detailed image survey of the ground below Perseverance. This was done so we would have a good idea what rocks and pebbles already exist down there before some more—from our bit carousel—join them in the not-so-distant future.

With this below-chassis, preliminary imaging, in hand, the team embarked on a maneuver with our I never imagined we would perform—ever. Simply put, we are returning the remaining contents of Sample Tube 261 (our latest cored-) back to its planet of origin. Although this scenario was never designed or planned for prior to launch, it turns out dumping a core from an open tube is a fairly straightforward process (at least during Earth testing). We sent commands up yesterday, and later on today the rover’s robotic arm will simply point the open end of the sample tube toward the surface of Mars and let gravity do the rest.

I imagine your next question is, “Why are you dumping out the contents of the sample tube?” The answer is that, at present, we are not certain how much cored rock continues to reside in Tube 261. And while this rock will never make my holiday card list, the science team really seems to like it. So if our plans go well with our pebble mitigation (see below), we may very well attempt to core “Issole” (the rock from which this sample was taken) again.

Which brings me to next steps in our pebble mitigation strategy: We’re sending up commands to the rover later today ordering it to do two rotation tests of the bit carousel. These tests (the first, a small rotation; the second, larger) will execute this weekend. Our expectations are that these rotations—and any subsequent movement—will help guide our team, providing them the necessary information on how to proceed. Still, to be thorough, we are also commanding the rover to take a second set of under-chassis images, just in case one or more pebbles happen to pop free.

We expect the data and imagery from these two rotation tests to be sent to Earth by next Tuesday, Jan. 18. From there, we’ll analyze and further refine our plans. If I had to ballpark it, I would estimate we’ll be at our current location another week or so—or even more if we decide to re- Issole.

So there you have it. The Perseverance team is exploring every facet of the issue to ensure that we not only get rid of this rocky debris but also prevent a similar reoccurrence during future sampling. Essentially, we are leaving no unturned in the pursuit of these four pebbles.



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Perseverance dumps contents of Sample Tube 261 in first step to clear rocky anomaly (2022, January 19)
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Hexbyte Glen Cove 2D materials combine, becoming polarized and giving rise to photovoltaic effect thumbnail

Hexbyte Glen Cove 2D materials combine, becoming polarized and giving rise to photovoltaic effect

Hexbyte Glen Cove

Tungsten selenide (WSe2) and black phosphorus (BP) do not exhibit polarized electronic behavior until combined such that their structures overlap. Credit: ©2021 Ideue et al.

For the first time, researchers have discovered a way to obtain polarity and photovoltaic behavior from certain nonphotovoltaic, atomically flat (2D) materials. The key lies in the special way in which the materials are arranged. The resulting effect is different from, and potentially superior to, the photovoltaic effect commonly found in solar cells.

Solar power is considered a key technology in the move away from fossil fuels. Researchers continually innovate more efficient means to generate solar energy. And many of these innovations come from the world of research. Research Associate Toshiya Ideue from the University of Tokyo’s Department of Applied Physics and his team are interested in the photovoltaic properties of 2D materials and their interfaces where these materials meet.

“Quite often, interfaces of multiple 2D materials exhibit different properties to the individual crystals alone,” said Ideue. “We have discovered that two specific materials which ordinarily exhibit no do so when stacked in a very particular way.”

The two materials are tungsten selenide (WSe2) and black phosphorus (BP), both of which have different crystal structures. Originally, both materials are nonpolar (do not have a preferred direction of conduction) and do not generate a photocurrent under light. However, Ideue and his team found that by stacking sheets of WSe2 and BP together in the right way, the sample exhibited polarization, and when a light was cast on the material, it generated a current. The effect takes place even if the area of illumination is far from the electrodes at either end of the sample; this is different from how the ordinary effect works.

Under laser illumination, the layered material generates a current. Credit: ©2021 Ideue et al.

Key to this behavior is the way the WSe2 and BP are aligned. The crystalline structure of BP has reflective, or mirror, symmetry in one plane, whereas WSe2 has three lines of mirror symmetry. When the symmetry lines of the materials align, the sample gains polarity. This kind of layer stacking is delicate work, but it also reveals to researchers new properties and functions that could not be predicted just by looking at the ordinary form of the materials.

“The biggest challenge for us will be to find a good combination of 2D materials with higher electric-generation efficiency and also to study the effect of changing the angles of the stacks,” said Ideue. “But it’s so rewarding to discover never-before-seen emergent properties of materials. Hopefully, one day this research could improve solar panels. We would like to explore more unprecedented properties and functionalities in nanomaterials.”

The study is published in Science.



More information:
A van der Waals interface that creates in-plane polarization and a spontaneous photovoltaic effect. Science, science.sciencemag.org/cgi/doi … 1126/science.aaz9146

Citation:
2D materials combine, becoming polarized and giving rise to photovoltaic effect (2021, April 1)
retrieved 1 April 2021
from https://phys.org/news/2021-04-2d-materials-combine-polarized-photovoltaic.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
part may be reproduced without the written permission. The content is provided for information purposes only.

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