You could say that the study of extrasolar planets is in a phase of transition of late. To date, 4,525 exoplanets have been confirmed in 3,357 systems, with another 7,761 candidates awaiting confirmation. As a result, exoplanet studies have been moving away from the discovery process and towards characterization, where follow-up observations of exoplanets are conducted to learn more about their atmospheres and environments.
In the process, exoplanet researchers hope to see if any of these planets possess the necessary ingredients for life as we know it. Recently, a pair of researchers from Northern Arizona University, with support from the NASA Astrobiology Institute’s Virtual Planetary Laboratory (VPL), developed a technique for finding oceans on exoplanets. The ability to find water on other planets, a key ingredient in life on Earth, will go a long way towards finding extraterrestrial life.
The research was conducted by postdoctoral researcher Dominick J. Ryan, a postdoctoral researcher at Northern Arizona University (NAU), and Tyler D. Robinson – an Assistant Professor of Astronomy and Planetary Science at NAU and the NASA Astrobiology Institute. The study that described their findings, titled “Detecting Oceans on Exoplanets with Phase-Dependent Spectral Principal Component Analysis,” recently appeared online and is being considered for publication by The Planetary Science Journal.
An artist’s illustration of the exoplanet HR8799e. The ESO’s GRAVITY instrument on its Very Large Telescope Interferometer made the first direct optical observation of this planet and its atmosphere. Credit: ESO/L. Calçada
When it comes to exoplanet characterization, the most promising technique is the Transit Method (aka. Transit Photometry). This consists of monitoring stars for periodic dips in brightness, which are indications of planets passing in front of their parent stars (relative to the observer). At times, astronomers are also able to obtain spectra as light passes through the transiting planet’s atmosphere, revealing things about its chemical composition. But as Prof. Robinson told Universe Today via email, this method doesn’t allow for surface observations:
“For now, our best techniques for characterizing rocky exoplanets do not tell us much about the surface environments for these worlds (including whether liquid water is present). For Hubble (and the soon-to-launch JWST), we use transit spectroscopy to characterize the atmospheres of exoplanets – looking for very slight changes in the brightness and color of a host star when a planet traverses its disk. In this geometry/setup, the very long paths the light takes through the atmosphere (most analogous to viewing the Sun at sunset on Earth) means that the deep atmosphere (and surface) is obscured.”
In the near future, this situation is expected to change considerably, thanks to next-generation instruments like the James Webb Space Telescope (JWST), and ground-based observatories like the Extremely Large Telescope (ELT). Thanks to their sophisticated optics, coronographs, and spectrometers, these telescopes will be able to directly image smaller exoplanets that orbit more closely to their stars (which is where potentially habitable rocky planets are more likely to be found).
Electrodes in Spacesuits Could Protect Astronauts from Harmful Dust on Mars
To quote NASA associate administrator Jim Reuter, sending crewed missions to Mars by 2040 is an “audacious goal.” The challenges include the distance involved, which can take up to six months to traverse using conventional propulsion methods. Then there’s the hazard posed by radiation, which includes increased exposure to solar particles, flares, and galactic cosmic rays (GCRs). And then there’s the time the crews will spend in microgravity during transits, which can take a serious toll on human health, physiology, and psychology.
But what about the challenges of living and working on Mars for several months at a time? While elevated radiation and lower gravity are a concern, so is Martian regolith. Like lunar regolith, dust on Mars will adhere to astronauts’ spacesuits and inflict wear on their equipment. However, it also contains harmful particles that must be removed to prevent contaminating habitats. In a recent study, a team of aerospace engineers tested a new electrostatic system for removing Martian regolith from spacesuits that could potentially remove harmful dust with up to 98% efficiency.
The new system was designed by Benjamin M. Griggs and Lucinda Berthoud, a Master’s engineering student and Professor of Space Systems Engineering (respectively) with the Department of Aerospace Engineering at the University of Bristol, UK. The paper that describes the system and the verification process recently appeared in the journal Acta Astronautica. As they explain, the Electrostatic Removal System (ERS) they propose utilizes the phenomenon of dielectrophoresis (DEP) to remove Martian dust from spacesuit fabrics.
Dust flies from the tires of a moon buggy, driven by Apollo 17 astronaut Gene Cernan. These “rooster-tails” of dust caused problems. Credit: NASA
Much like its lunar counterpart, Martian regolith is expected to be electrostatically charged due to exposure to cosmic radiation. But on Mars, there’s also the contribution made by dust devils and storms, which have been known to generate electrostatic discharges (aka. lightning). During the Apollo missions, astronauts reported how the lunar regolith would adhere to their suits and get tracked back into their Lunar Modules. Once inside, it would similarly stick to everything and get into their eyes and lungs, causing irritation and respiratory problems.
Given their plans to return astronauts to the Moon through the Artemis Program, NASA is investigating several methods to prevent regolith from getting into habitation modules – like coating technology for spacesuits and electron beams for cleaning them. While Martian dust is expected to inflict similar wear on spacesuits, the situation is made worse because it may contain toxic particles. As Griggs explained to Universe Today via email:
“Beyond having an abrasive effect on spacesuits themselves, Martian regolith is also expected to present health issues to astronauts. It is known to contain a range of harmful particles which may be carcinogenic or cause respiratory issues, and data from the Pathfinder mission showed the presence of toxic particles such as chromium. Martian regolith will therefore require removal from spacesuits prior to entry into habitation zones on Mars to prevent contact between astronauts and regolith particles.”
The principle behind the device, dielectrophoresis (DEP), refers to the movement of neutral particles when subjected to a nonuniform electric field. Their proposed Electrostatic Removal System (ERS) comprises two components: a High Voltage Waveform Generator (HVWG) used to produce square waves of varying frequencies and amplitudes up to 1000 volts and an Electrostatic Removal Device (ERD) consisting of an array of parallel copper electrodes. When the square waves are applied across the electrodes in the ERD, a large and varying electric field is generated. As Griggs summarized:
“Therefore, when dust particles are incident on the surface of the ERD, the dust particles are displaced through a combination of electrostatic and dielectrophoretic forces (due to the large electric field), which acts on charged and uncharged particles respectively within the dust. This acts to displace dust particles in a direction perpendicular to the electrodes, resulting in the clearing of the ERD surface.”
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If Exoplanets Have Lightning, it’ll Complicate the Search for Life
Discovering exoplanets is almost routine now. We’ve found over 5,500 exoplanets, and the next step is to study their atmospheres and look for biosignatures. The James Webb Space Telescope is leading the way in that effort. But in some exoplanet atmospheres, lightning could make the JWST’s job more difficult by obscuring some potential biosignatures while amplifying others.
Detecting biosignatures in the atmospheres of distant planets is fraught with difficulties. They don’t advertise their presence, and the signals we receive from exoplanet atmospheres are complicated. New research adds another complication to the effort. It says that lightning can mask the presence of things like ozone, an indication that complex life could exist on a planet. It can also amplify the presence of compounds like methane, which is considered to be a promising biosignature.
The new research is “The effect of lightning on the atmospheric chemistry of exoplanets and potential biosignatures,” and it’s been accepted for publication in the journal Astronomy and Astrophysics. The lead author is Patrick Barth, a researcher from the Space Research Institute at the Austrian Academy of Sciences.
While we’ve discovered over 5,500 exoplanets, only 69 of them are in the potentially habitable zones around their stars. They’re rocky planets that receive enough energy from their stars to potentially maintain liquid water on their surfaces. Our search for biosignatures is focused on this small number of planets.
This is an artist’s illustration of the exoplanet TRAPPIST-1d, a potentially habitable exoplanet about 40 light-years away. Planets like these are prime targets for JWST’s spectrometry. Image Credit: By NASA/JPL-Caltech – Cropped from: PIA22093: TRAPPIST-1 Planet Lineup – Updated Feb. 2018, Public Domain, https://commons.wikimedia.org/w/index.php?curid=76364484
The important next step is to determine if these planets have atmospheres and then what the composition of those atmospheres is. The JWST is our most powerful instrument for these purposes. But in order to understand what the JWST shows us in distant atmospheres, we have to know what its signals tell us. Research like this helps scientists prepare for the JWST’s observations by alerting them to potential false positives and masked biosignatures.
This JWST spectra isn’t part of this research, but it shows how the powerful space telescope can
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Titan Probably Doesn’t Have the Amino Acids Needed for Life to Emerge
Does Saturn’s largest moon, Titan, possess the necessary ingredients for life to exist? This is what a recent study published in Astrobiology hopes to address as a team of international researchers led by Western University investigated if Titan, with its lakes of liquid methane and ethane, could possess the necessary organic materials, such as amino acids, that could be used to produce life on the small moon. This study holds the potential to help researchers and the public better understand the geochemical and biological processes necessary for life to emerge throughout the cosmos.
Along with its liquid lakes of methane and ethane, Titan is also strongly hypothesized to possess a subsurface liquid water ocean like Saturn’s icy moon, Enceladus, and Jupiter’s icy moon, Europa. For the study, the researchers used data from impact cratering from comets to estimate the number of organic molecules that could relocate from Titan’s surface to its subsurface liquid water ocean. The team hypothesized that when comets strike Titan’s surface, their icy materials would melt from the heat of the impact and mix with the surface organics, resulting in a unique mixture. However, the heavier liquid water would then sink to the subsurface, slowly filling the subsurface ocean over time.
Artist’s cutaway illustration displaying Titan’s subsurface ocean (blue). (Credit: NASA/JPL)
After accounting for a presumed annual number of cometary impacts on Titan’s surface throughout its billions of years of existence, the researchers then calculated how much water would make its way from the surface to the subsurface ocean. In the end, the team concluded that the amount of glycine, which is the most basic amino acid that forms the proteins to create life, was measured at no greater than 7,500 kilograms/year (16,530 pounds/year). This amount approximately equals the size of a smaller African forest elephant, hence indicating number of organic materials that exist on Titan is quite miniscule.
“One elephant per year of glycine into an ocean 12 times the volume of Earth’s oceans is not sufficient to sustain life,” said Dr. Catherine Neish, who is an associate professor in the Department of Earth Sciences at Western University and lead author of the study. “In the past, people often assumed that water equals life, but they neglected the fact that life needs other elements, in particular carbon.”
While Dr. Neish’s study presents somewhat dire implications for finding life on Titan, this study comes on the heels of a recent investigation into how organic hazes on ancient Earth could have contained the necessary building blocks of life, including nucleobases and amino acids, which could hold implications for finding life on Titan due to the moon’s hazy atmosphere. For this study, the researchers used laboratory experiments to determine that “warm little ponds” on ancient Earth could host nucleobases. Both studies offer profound insights into the processes responsible for both creating and sustaining life beyond Earth, and further research is undoubtedly required to better understand these processes.
One such research opportunity that could help solidify these studies could be NASA’s upcoming Dragonfly mission, which is a quadcopter designed to search Titan’s surface for signs of potential habitability with Dr. Neish assigned as a mission co-investigator. Dragonfly currently has a scheduled launch date of July 2028, arriving at Saturn’s largest moon sometime in 2034. While Dragonfly will not be the first aircraft on another world, as that honor goes to NASA’s Ingenuity Mars Helicopter, it will be the first aircraft to land and operate in the outer solar system. Dragonfly will launch more than 20 years after the European Space Agency’s Huygens probe landed on Titan in January 2005, beaming back images of rounded rocks that could have formed from liquid processes.
What new discoveries will scientists make about Titan and its potential for life in the coming years and decades? Only time will tell, and this is why we science!
As always, keep doing science & keep looking up!
The post Titan Probably Doesn’t Have the Amino Acids Needed for Life to Emerge appeared first on Universe Today
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