NASA is partnering with eight U.S. companies to advance small spacecraft and launch vehicle technologies that are on the verge of maturation and are likely to benefit both NASA and the commercial space market.
February 22, 2017
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2017年2月22日 星期三
Temperate Earth-Sized Planets Found in Extraordinarily Rich Planetary System TRAPPIST-1
Temperate Earth-Sized Planets Found in Extraordinarily Rich Planetary System TRAPPIST-1 , ESO
"Astronomers have found a system of seven Earth-sized planets just 40 light-years away. Using ground and space telescopes, including ESO's Very Large Telescope, the planets were all detected as they passed in front of their parent star, the ultracool dwarf star known as TRAPPIST-1. According to the paper appearing today in the journal Nature, three of the planets lie in the habitable zone and could harbour oceans of water on their surfaces, increasing the possibility that the star system could play host to life. This system has both the largest number of Earth-sized planets yet found and the largest number of worlds that could support liquid water on their surfaces."
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NASA Telescope Reveals Largest Batch of Earth-Size, Habitable-Zone Planets Around Single Star
NASA's Spitzer Space Telescope has revealed the first known system of seven Earth-size planets around a single star. Three of these planets are firmly located in the habitable zone, the area around the parent star where a rocky planet is most likely to have liquid water.
February 22, 2017
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February 22, 2017
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Wonderful potentially habitable worlds around TRAPPIST-1
Wonderful potentially habitable worlds around TRAPPIST-1
Posted by Franck Marchis
22-02-2017 12:00 CST
Topics: extrasolar planets
This post originally appeared on Franck Marchis' Cosmic Diary blog and is reposted here with his permission.
In May 2016, Michael Gillon and his team announced the discovery of three Earth-sized exoplanets around TRAPPIST-1, an ultra cool M-dwarf star, using the small TRAPPIST telescope at ESO-La Silla, Chile. It was an exciting discovery—yet on that day no one could possibly have imagined that less than a year later they would make another significant discovery involving the same system. But here we are: today, they announced in Nature the discovery of seven Earth-size worlds, three of which lie in the habitable zone and could support liquid water on their surfaces.
NASA / JPL-Caltech
The TRAPPIST-1 system: Where might liquid water exist?
This representation of the Trappist-1 system shows which planets could harbor liquid water. The inner three planets are likely too hot, and the outer planet is probably too cold, but the middle three planets might be just right.
The star, named TRAPPIST-1, is a fairly inconspicuous star in our Milky Way. Small (8% the mass of the sun) and cold (half the temperature of the sun), it is a member of an ultra-cool dwarf population that represents 15% of the star population of our galaxy. In 2016, Gillon and his team detected the transit (i.e., the shadow of a planet passing between its host star and us) of three exoplanets at the inner edge of the habitable zone of their star.
Energized and excited by this discovery, the team requested and received additional telescope time to follow up on this system during the second half of 2016. The NASA Spitzer telescope is one of the facilities they selected for an ambitious program that called for monitoring the TRAPPIST-1 system almost continuously for twenty days. Spitzer and other ground-based telescopes allowed the team to detect thirty-four transits, more than they had anticipated, suggesting the existence of additional exoplanets in the system.
After an careful analysis, the data revealed the presence of seven Earth-sized exoplanets (named TRAPPIST 1b, c, d, e, f, g, and h) in orbit around this M-type star. Because their orbital periods are short (less than twelve days for planets b to g), several transits were detected during the campaign. Accurately measurements of those tiny events (0.6% dimming of the star) provide a wealth of information about the planets’ orbits, sizes, and even masses by measuring precisely the timings of the transits which are perturbed by the gravity of other planets.
F. Marchis & H. Marchis
Trappist-1 top view
Top view of the Trappist-1 planetary system showing the circular orbits of the seven Earth-like exoplanets. The red dwarf is not to scale. The green area corresponds to the habitable zone of the star where liquid water could exist on the surface of those worlds.
So what have we learned about the TRAPPIST-1 system?
- It’s very tight; the most distant planet (h) is at 0.06 AU from its star. The closest one is at 0.01 AU. For comparison, Mercury orbits at 0.39 AU from our sun. This is NOT equivalent to our solar system, but more a minuscule version of it, comparable in size/mass ratio to Jupiter and its Galilean Moons.
- Similar to our solar system, these exoplanets travel circular orbits all of which go in the same direction. They probably formed more than 500 million years ago together with their star.
- The depth of the transits provides a measurement of the radius of the planets, which are similar to Earth (b, c, e, f, g) or Mars (d, h) so they range from 75% to 110% the size of Earth.
- The data are accurate enough to detect mutual gravitational effects, so we can infer the mass of the first six planets, and hence their density. Those are rocky worlds that range in density from 60 and 117% that of Earth.
- Considering the amount of energy they receive from the star, these planets might have a temperature suitable for the presence of liquid water on their surface (e,f,g) if we assume a similar atmosphere than Earth.
F. Marchis & H. Marchis
Trappist-1 incident flux and radiuses
Incident flux received by the exoplanets of Trappist-1, and their radiuses. For comparison, the incident flux of Mercury, Mars and Ceres, as well as the locations of Venus and Mars are added. Trappist-1d receives the same amount energy as Earth.
What can’t we say about the TRAPPIST-1 system?
- This is not the first discovery of a system with this many exoplanets. HR8832 and HD10180 have seven planets that were discovered by radial velocity. In both cases, the exoplanets are massive, at least ten times the mass of Earth. The host stars also have a mass similar to our sun. Kepler-90 is another system with seven exoplanets discovered by transit measurements. Several of those exoplanets are larger than Earth and probably ice and gas giants. What is crucial here is that for the first time, we have discovered seven temperate rocky exoplanets in orbit around a M-dwarf star. There are many such stars in our galaxy, so there are probably a lot of worlds like these out there!
- No, we have not yet discovered a cousin of Earth, much less seven of them. The measurements provide interesting information about these exoplanets, and we can confidently say that six of them are rocky. However, their location in the habitable zone of their star does not imply that they are habitable. For instance, Mars and Venus are in the habitable zone of our Sun, but are not habitable anymore. In other words, it is too early to say if there are oceans on their surface. TRAPPIST-1 is located twenty-nine light-years from us, so we will probably need the large aperture of the JWST or a dedicated space telescope like ARIEL to detect the presence of an atmosphere and derive its composition. Using the Hubble Space Telescope, the team has tried to detect an exosphere on one of the planets but without success so far.
- No, we have not detected life on those exoworlds. In my opinion, life is the result of a complex cascade of random events, and we don’t really know if those exoplanets, located near an ultra-cool star, are suitable for life. They are very close to their star and may be tidally locked, showing the same hemisphere to their star at all times. The existence of life on worlds with temperatures that vary from one hemisphere to the other is difficult to imagine. It will take years of observations and modeling to understand if life can exit on such a strange worlds.
NASA / JPL-Caltech / F. Marchis
The TRAPPIST-1 system
Artist's representation of the Trappist-1 system with the exoplanets at scale between each other and the host red dwarf star. The ESI (Earth Similarity Indice) calculated by Abel Mendez (PHL) for each exoplanet is added. For comparison with our solar system planets, Earth's ESI is 1, Venus's ESI is 0.44, and Mars's ESI is 0.64. Caution: the ESI is not a direct measure of habitability but formally a fuzzy comparison, using a distance metric, between a selected set of planetary properties of a planet and Earth. See http://ift.tt/1eRmxYv for more information.
Last year, astronomers announced the discovery of a potentially terrestrial planet around Proxima Centauri, located only 4.2 light-years away from us. Today, this group reveals the existence of seven potentially habitable worlds around a small star that could live forever. The field of exoplanet is without doubt booming, and it is not over.
A team led by Emmanuel Jehin, co-author of the paper, is currently building Speculoos, a TRAPPIST telescope “on steroids”, made of four, 1-meter robotic telescopes installed at Cerro Paranal. With this telescope, the team will survey 10 times more red dwarfs than TRAPPIST did. So we could expect the discovery of a dozen systems similar to this one soon. We will have the opportunity to explore the diversity of atmospheres and climates on Earth-like worlds, and potentially life out there.
The discovery of these strange new worlds where life could flourish is the beginning of an exciting time for astronomers and biologists. A time when we are beginning to see the unimaginable, a time when life as we don’t know it can be imaged and studied. We will probably need to build complex and expensive instruments to understand those worlds—but what an astonishing, awe-inspiring, life-changing prize to win, don’t you think?
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An asteroid or comet headed for Earth is the only large-scale natural disaster we can prevent. Working together to fund our Shoemaker NEO Grants for astronomers, we can help save the world.
Pretty pictures and
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Sounding Rocket Launches to Study Auroras
A NASA Black Brant IX sounding rocket soars skyward into an aurora over Alaska following a 5:13 a.m. EST, Feb. 22, 2017 launch from the Poker Flat Research Range in Alaska. The rocket carried an Ionospheric Structuring: In Situ and Groundbased Low Altitude StudieS (ISINGLASS) instrumented payload examining the structure of an aurora. via NASA http://ift.tt/2lp4hz6
ISS Daily Summary Report – 2/21/2017
Preparation for Dragon Arrival: Dragon successfully lifted off on the SpaceX Falcon 9 rocket from Launch Pad 39A at Kennedy Space Center, Florida Sunday 19-February at 8:39 am CST. Today Dragon will continue to phase towards the ISS for a planned capture on Wednesday 22-February at approximately 5:00 am CST. Onboard the ISS the USOS crew participated in a Dragon cargo transfer conference with ground specialist. Miniature Exercise Device (MED-2): The crew was unable to locate the one-of-a-kind power cable and stood down from MED-2 technical evaluation operations while ground teams investigated the potential locations. The crew was able to provide input for potential placement of cameras for future MED-2 exercise investigations. The microgravity environment of space weakens muscle and bone, so orbiting crew members spend significant amounts of time exercising. The ISS’s exercise equipment is large and bulky, while the MED-2 aims to demonstrate small robotic actuators can provide motion and resistance for crew workout sessions, reducing the size and weight of exercise equipment for long-duration space missions. The MED-2 investigation is a system to test key technologies needed to develop space based exercise equipment that may provide appropriate countermeasures to the adverse effects of microgravity. This technology is critical for the initial design and development of second and third generation Counter Measure Systems (CMS) hardware that is an order of magnitude lighter and smaller than existing ISS class of CMS hardware and that has significantly greater reliability. Radio Frequency Identification (RFID) Tag Installation and Calibration: Last week the crew installed the RFID antennas around the hatchways of the US Lab, Node 1 and Node 2, which are continuously scanning to measure the RFID tags that are transported through the hatchways and modules. Today the crew installed 16 marker tags in each the US Lab, Node 1 and Node 2 in a roughly uniform distribution throughout the module. The crew then performed a calibration by attaching an RFID tag to a video camera. They then translated through the three modules at different rates of speed. Ground teams will then take the time-tagged video data and RFID collected data to calibrate the antennas. The RFID Logistics experiment aims to utilize RFID enabled tags on hardware throughout the ISS, and assist in the tracking of the hardware as it is moved around the station. Combustion Integration Rack (CIR) Camera Cover Removal: The crew translated and rotated the CIR Optics Bench in order to access the Intensified Camera Package. They uninstalled the camera at Universal Mounting Location-2 (UML-2) at the back of the Optics Bench and removed the CIR Soft Window cover. The Intensified Camera Package was reinstalled and Optics Bench rotated back into position. During a ground checkout on February 10, teams were unable to complete a calibration of the camera packages for the Cool Flames Experiment. After investigation by ground specialists it was determined that the Window Cover was still attached. Teams will resume checkout and calibration activities of thee CIR for the Cool Flames experiment following today’s completed activities. The Cool Flames Investigation will provide new insight into the phenomenon where some types of fuels initially burn very hot, then appear to go out — but they continue burning at a much lower temperature, with no visible flames (cool flames). Understanding cool flame combustion helps scientists develop new engines and fuels that are more efficient and less harmful to the environment. Microgravity Science Laboratory (MSL) Sample Cartridge Assembly (SCA) Exchange: The crew changed out the SCA in the Solidification Quenching Furnace (SQF), removing the calibration cartridge and inserting the first test sample. Ground teams will initiate the runs next week. The Batch-2b of the Materials Science Laboratory Sample Cartridge Assemblies serves two projects investigating how different phases organize in a structure when metallic alloys are solidified. The project Metastable Solidification of Composites (METCOMP) studies the phase formed by the reaction of the remaining liquid phase with an already formed solid, to form a second solid phase on cooling. For this purpose, Bronze (Copper-Tin Alloys) of different compositions will be processed. The other project, Solidification along a Eutectic path in Ternary Alloys (SETA), looks at how two phases that form together organize into lamellar, or fiber, structures when cooling Aluminum (Copper-Silver Alloys). Both projects will provide benchmark samples that will enable to test numerical models that aim to predict these structures. Lighting Effects Vision Test: The crew performed a Visual Performance Test in which they configured the Solid State Lighting Assembly (SSLA) in their Crew Quarters (CQ) to the correct mode, turning off all other light sources, then performed one Numerical Verification Test and one Color Discrimination Test. The Lighting Effects investigation studies the impact of the change from fluorescent light bulbs to solid-state light-emitting diodes (LEDs) with adjustable intensity and color and aims to determine if the new lights can improve crew circadian rhythms, sleep, and cognitive performance. Microscope Setup: In support of the Microgravity Expanded Stem Cells (MESC) payload to be delivered by SpX-10 the crew configured a microscope outside the Microgravity Science Glovebox (MSG). MESC will aid researches determine the efficiency of using a microgravity environment to accelerate expansion (replication) of stem cells for use in terrestrial clinical trials for treatment of disease. Haptics-2: During today’s Haptics-2 experiment the 1-Degree of Freedom (1-DOF) joystick failed. No resistance was felt when moving the handle without pressing the yellow activation button. When the crew pressed the activation button and moved the joystick an off-nominal mechanical/electrical sound was heard, suggesting a possible mechanical failure. Teams decided to stand down for operations and downlink the log files to investigate the issue. Haptics-2 is a technology demonstration experiment aimed at validating control interactions to take place between space and ground. In particular, this experiment allows for an astronaut crew in space to control, in real-time, robotic assets on Earth, using force feedback. The operational experience gained from Haptics-2 could be vital for future exploration missions beyond Earth orbit, where astronauts would be able to control robotic assets to maximize scientific operations […]
February 22, 2017 at 12:00AM
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2017年2月21日 星期二
NASA's audacious Europa missions are getting closer to reality
NASA's audacious Europa missions are getting closer to reality
Posted by Jason Davis
21-02-2017 15:43 CST
Topics: Europa, Europa lander, Europa Clipper
NASA is boldly going to Europa—hopefully.
Two separate missions to send a flyby spacecraft and lander to Jupiter's ocean-harboring moon are steadily gaining steam. Today, NASA said the flyby craft, internally dubbed the Europa Clipper, has officially entered the preliminary design phase, having cleared a program milestone called Key Decision Point B. The lander also took another step toward reality earlier this month, when a team of scientists formally delivered a report laying out the mission's science goals and some overall engineering concepts.
Together, the missions would attempt to discover whether Europa was habitable, and directly search for signs of life—something NASA hasn't done since the Viking missions to Mars in the mid-1970s.
Neither mission is fully funded. And even in a best-case scenario, the lander mission wouldn't touch down on Europa until 2031 or 2032, meaning it could be 15 years before we know whether something is swimming under Europa's icy crust. Will the wait pay off? I spoke with two experts about this audacious pair of spacecraft, and looked into what needs to happen to make them a reality.
NASA / JPL-Caltech
Europa Clipper concept
NASA's Europa Clipper mission would launch as early as 2022 and assess the habitability of Europa, paving the way for a future separate lander mission.
The Clipper
The first thing I learned about the Europa Clipper is that the spacecraft's name is more than a mere nod to the romantic sailing ships of yesteryear—it's an apt description of how the mission works.
The radiation environment around Jupiter is hard on spacecraft, due to the planet's large magnetic field, which traps charged particles from the sun. Rather than orbiting Europa in the heart of that radiation, the Clipper will fly around Jupiter in large, egg-shaped orbits that are mostly outside the harmful radiation belts. Over the course of two to three years, the Clipper will dive into the radiation 45 times, whizzing past Europa to gather data before the spacecraft then, as Dipak Srinivasan puts it, "gets out of Dodge."
Srinivasan is the RF telecommunications lead for Clipper at the Johns Hopkins University Applied Physics Laboratory. He told me the spacecraft will behave like an ancient sailing ship speeding between trade stops. After a Europa flyby, the Clipper will spend about three weeks in safe harbor beyond Jupiter's radiation, transmitting science data back to Earth. Srinivasan said these signals serve double duty: Not only do they carry mission data, ground controllers measure their Doppler shifts to pinpoint the spacecraft's location.
The Clipper mission's goal is to assess whether Europa is habitable.
"We really want to understand the composition of Europa's interior and exterior, and see whether that composition is commensurate with what we think is required for life," Srinivasan said.
Europa is slightly smaller than Earth's Moon. Its surface is an icy shell 25 kilometers thick, sitting atop an ocean about 100 kilometers deep that contains twice as much water as our own. Scientists suspect the ocean is salty, and stays liquefied because of the immense tidal forces exerted by mighty Jupiter.
"Wherever there's water on Earth, there's life," said Srinivasan. "Given the fact that there is liquid water on Europa, and the fact that it's been there for billions of years, makes it one of the likeliest places for life in our solar system."
During each flyby, the Clipper will scan Europa with an array of science instruments. There's an ice-penetrating radar, a magnetometer to measure the ocean's salinity, and a thermal camera to look for warm spots near the surface. Other instruments will examine plumes of saltwater that may periodically spray into space. Cameras aboard the Clipper will deliver views of the surface in resolutions up to a meter per pixel; our best views of Europa so far come from the Galileo mission, and have a maximum resolution of 6 meters per pixel.
The mission is being jointly developed between the JHU Applied Physics Laboratory and NASA's Jet Propulsion Laboratory.
"It's kind of neat," Srinivasan said. "You have an all-star cast of people across both institutions, both of which have significant deep space experience. You're kind of pulling from a really, large bench and you're coming up with really, clever solutions on how to make this work."
NASA / JPL-Caltech
Europa lander concept
The conceptual design for NASA's proposed Europa lander.
The Lander
In June 2016, NASA convened a science definition team, or SDT, to investigate what kind of questions a lander could answer on the surface of Europa. The SDT was also tasked with defining some of the lander's high-level engineering and instrument requirements.
Earlier this month, the SDT released its 264-page report, with this grin-inducing quote on page six:
"Europa may hold the clues to one of NASA's long standing goals—to determine whether or not we are alone in the universe. The highest-level science goal of the mission presented here is to search for evidence of life on Europa."
The implications of that goal—which was set by officials at NASA headquarters—are stunning. The agency has not directly searched for life on another world since the Viking missions to Mars in the mid-1970s. The dual Viking landers contained three biological experiments that tried to metabolize soil samples. The results were inconclusive, and in the decades since, there has been a lot of debate on how to go about detecting extraterrestrial lie.
Deciding how a Europa lander would search for life was "a little surreal," said Sarah Hörst, a planetary scientist and assistant professor at Johns Hopkins University who served on the SDT.
"Would this be life? What is life? It's not a conversation I normally have on a daily basis," she told me.
For guidance, the team included experts familiar with subglacial lakes in Antarctica, and scientists who study extremophiles—organisms that thrive in some of the harshest conditions on Earth.
The Europa lander would collect five, 7-cubic-centimeter surface samples, scraped from 10 centimeters below the surface. The samples would be analyzed with a suite of instruments, including a gas chromatograph and mass spectrometer to detect organics, a microscope system to look for microbial cells, and an ultraviolet spectrometer to characterize possible organic material.
It would likely take a combination of measurements, said Hörst, to conclude life might be present.
"As far as we know, right now there's one measurement where you say, 'Okay, if we measure that, then there's life,'" she said.
Since the lander's samples would only come from 10 centimeters below Europa's radiation-flooded surface, what are the chances of finding anything alive?
Hörst said reconnaissance work by the Clipper spacecraft might yield younger sections of ice that have been bombarded by less radiation. Additionally, not all areas of the moon are irradiated at the same level. Europa, like Earth's moon, is tidally locked, meaning the same side always faces Jupiter.
And even if the lander scoops up some life that, as Hörst puts it, is "no longer intact," there might be leftover chemical footprints showing something was once there.
"Even samples that have been highly radiation-processed on Earth still retain chemical signatures that you could interpret as a evidence of life," she said.
NASA / JPL / Ted Stryk
Europa in color: trailing hemisphere
Galileo captured this global view of Europa on its 10th orbit of Jupiter, on September 19, 1997.
When and how?
NASA officials say the Clipper mission is still on track for a mid-2022 launch.
Using a powerful boost from NASA's new heavy lift rocket, the Space Launch System, the Clipper would fly directly to Jupiter and arrive in 2025. Without SLS, the journey would take five years longer, and require flybys of Venus and Earth to reach the right trajectory.
Flying past Venus means flying closer to the Sun. Flying closer to the Sun means extra heat shielding. And extra heat shielding means a heavier spacecraft. Though Congress has ordered NASA to use SLS for both the Clipper and lander missions, the agency is still keeping the extra heat shielding in the Clipper's design for now—just in case anything derails development of the yet-to-be-flown rocket.
Without SLS, the lander as currently designed might not be able to fly at all, according to the SDT report. That's because the spacecraft will be heavy. In addition to the lander itself, there are three other components: a carrier and relay stage, a de-orbit stage, and a descent stage. Officials aren't publicly saying how heavy the entire package might be, but it would currently require a deep space thruster burn and Earth gravity assist to put it on the correct path to Jupiter—even with the added boost from SLS. The earliest the lander would launch is 2024 or 2025, putting it at Jupiter around 2030.
Once in orbit around Jupiter, the lander spacecraft would spend 18 months slowly spiraling inward to Europa, swinging past Callisto and Ganymede on the way. At Europa, the carrier and relay orbiter would separate and act as a data relay satellite. The Clipper, ideally still operating in an extended mission, would be used as a backup relay. The lander would not have the capability to talk to Earth on its own.
Remember the Curiosity spacecraft's seven minutes of terror, during which it plunged to the Martian surface in a harrowing process known as entry, descent and landing, or EDL? Since Europa has no atmosphere, and the descent begins in orbit, a new acronym is in play: DDL, which stands for de-orbit, descent and landing.
First, the de-orbit stage will pull the descent stage and lander out of orbit. As the thruster-powered descent stage approaches the surface, it will perform the same skycrane maneuver that deposited Curiosity onto Mars, where a tether lowers the lander. The descent stage then cuts loose and flys away for an intentional crash-landing.
Once the lander is safely on the surface, scientists will have to work fast to gather their data. The spacecraft is powered only by a 45-kilowatt-hour battery designed to last between 20 to 40 days. Why not find a way to stay longer? Because the carrier relay orbiter, which will be bathed in Jupiter's radiation, is expected to fail in just a single a month.
Awaiting the greenlight
Federal fiscal year 2017 began back on October 1, 2016, but Congress has not yet passed a 2017 budget. As of now, with the notable exception of Orion and the Space Launch System, NASA is operating under 2016 funding levels.
In 2016, Congress earmarked $175 million for the Clipper mission. In proposed 2017 spending bills, the House allocated $260 million to be used for both the Clipper and lander, while the Senate did not mention the missions at all. One source I spoke with said NASA is internally estimating a cost of $2 billion for the Clipper alone, and that doesn't include the cost of the rocket, the Space Launch System, which could have have a price tag between $500 million and $1 billion, according to statements by various NASA officials.
That means that despite the progress, there are a lot of hurdles to overcome before humanity gets a chance to search for life on Europa. But NASA missions have endured far worse; for one example, look no further than the 16-year struggle to get the New Horizons mission to Pluto on the launchpad.
And in this case, the end result could be a confirmation of life beyond Earth.
"Just imagine if that ends up being the case," Srinivasan said. "That's transformative, to be able to say that we lived in a time when that discovery was made."
See other posts from February 2017
Or read more blog entries about: Europa, Europa lander, Europa Clipper
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