Category: Other Worlds and Tech

Space Sunday: a ring of fire, 6 billion Earths and an FRB

Posted on by Inara Pey
The “ring of fire” of the June 21st annular eclipse as seen from Taiwan. Credit: unknown, distributed via Twitter.

For parts of East Africa, the Middle East and Asia, the 2020 summer solstice of June 21st was marked by an annular eclipse of the Sun.

Solar eclipses – when the Moon passes between the Earth and the Sun – take a number of forms, of which the most spectacular is, of course, a total eclipse. These occur when the distance between the Earth and the Moon is such that entire disk of the Sun is covered by the Moon, and the Moon’s shadow – called the umbra – falls directly onto the Earth’s surface, reducing the landscape directly below it to a state of dusk-like darkness called Totality. And just before that period of Totality, that can last several minutes, the solar corona is displayed as a beautiful halo of pearly white light.

A combination of pictures showing the June 21st eclipse as seen from (top l to r) Kurukshetra, Allahabad, Bangalore; (bottom l to r) Kolkata, New Delhi, Bangalore. Credits: Jewel Samad, Manjunath Kiran, Sanjay Kanojia, Dibyangshu Sarkar, Sajjad Hussain/AFP via Getty Images

However, as the Moon’s orbit around the Earth is elliptical rather than circular, for a total eclipse to occur, the Moon needs to be around 379,100 km from Earth. At this distance, the conical shadow of the Moon (the umbra) is sufficient for us to witness Totality. When the Moon is further away from Earth – say at the 381,500 km of the June 21st, 2020 event – , we have an annular eclipse, in which the Moon’s umbra “falls short” of reaching the Earth’s surface. This means that only around 99-99.5% of the Sun’s disk is covered by the Moon when observed along the path of the umbra, leaving the Sun and Moon appearing as a “ring of fire” hanging in the sky. It is this “ring of fire” that makes an annular eclipse the second most spectacular type of solar eclipse.

The needle of the Burj Khalifa, Dubai, magnificently set against the backdrop of the June 21st 2020 eclipse. Credit: unknown, distributed via Twitter

This particular event began at 03:45 UTC on June 21st, 2020, with the Moon “cutting in” to the disk of the Sun, and ended at 10:34 UTC as the Moon moved clear of the Sun. However, the period of maximum eclipse – the time at which the “ring of fire” might be seen – occurred at 06:54 UTC and was visible along a narrow track of the eclipse path just 21 km wide for around 35-60 seconds. Even so, it was still spectacular for those who witnessed it.

For people north and south of this narrow band of passage, the eclipse varied in nature from a partial ring of fire (where the disk of the Moon is jut off-centre enough relative to the Sun for the ring not to be completed) to a partial eclipse (where the disk of the Moon partially sits between the Earth and the Sun, but leaves a fair amount of the latter visible.

As direct viewing of the Sun is dangerous, ahead of the event, Astronomers Without Borders – a global group based out of the United States – worked with regional governments and astronomical groups and societies in Africa to get 16,000 pairs of solar glasses distributed to help people view the eclipse safely. For those well outside the path of the event who wished to witness it, the eclipse was streamed through You Tube and other platforms by a number of organisations such as SLOOH.

The track of the June 21st 2020 eclipse. The central orange band marks the track  along with the “ring of fire” could be seen. Credit: timeanddate.com

Eclipses are seasonal in nature, and generally occur in pairs: one lunar – when the Earth is between the Sun and the Moon, so that the later moves within the Earth’s shadow. This annular solar eclipse was preceded by a penumbral lunar eclipse on June 5th. However, and somewhat unusually, it will be followed by a further penumbral lunar eclipse on July 4th / 5th. A penumbral eclipse is one where the Moon is only within the outermost extent of the cone of Earth’s shadow, dimming it as it reflects the Sun’s light, rather than blocking sunlight falling on it entirely.

The next pair of eclipses will take place in November / December 2020, with a penumbral lunar eclipse on November 30th and a total solar eclipse visible from Chile and Argentina occurring on December 14th. For now, here’s a video of the June 21st event.

Six Billion Earths?

A new study from the University of British Columbia estimates that there could be as many as six billion Earth-type planets in the Milky Way galaxy orbiting within the habitable zone of stars with the same G_Type spectral class as our own Sun.

This may seem a surprisingly high number, but it requires context. In this case, it is estimated our galaxy has 400 billion stars of which some seven percent are G-Type. This means that if the study’s findings are correct, Earth-type planets orbiting in the habitable zone of G-Type stars averages out as just 0.18 per star.

Could Earth have as many as 6 billion “cousins” orbiting G-Type stars? Credit: NASA

The study findings are based on extrapolations from the data on 200,000 stars in the Kepler Space Telescope catalogue, with some adjustments to calculations.

The adjustments were required because Kepler used the transit method of exoplanet detection: watching for regular dips in a star’s brightness. However, given that a large planet will cause a correspondingly greater dip in a star’s brightness than one the size of Earth, the Kepler data is naturally biased towards finding larger planets. Further, it is possible that the dips caused by Earth-sized worlds could be mistaken for transient data rather than actual planets. So to handle things, Michelle Kunimoto, one of the researchers in the study used a technique called forward modelling.

I started by simulating the full population of exoplanets around the stars Kepler searched. I marked each planet as ‘detected’ or ‘missed’ depending on how likely it was my planet search algorithm would have found them. Then, I compared the detected planets to my actual catalogue of planets. If the simulation produced a close match, then the initial population was likely a good representation of the actual population of planets orbiting those stars.

– Michelle Kunimoto, University of British Columbia

Continue reading “Space Sunday: a ring of fire, 6 billion Earths and an FRB” →

Space Sunday: a touch of astronomy

Posted on by Inara Pey

 

Images of Proxima Centauri (l) and Wolf 359 (r) captured by NASA’s New Horizons spacecraft 7 billion km from Earth, are overlaid against images taken of the two stars from Earth-based telescopes, showing how the stars appear to “move” depending on the viewpoint. Credit: NASA

For the first time in history, a spacecraft has been used to demonstrate parallax as it applies to the stars – and in the process, underlining the fact that the constellations beloved of astrology are little more than a matter of line-of-sight as  seen from Earth.

The spacecraft in question is New Horizons, the mission that performed a fly-by of Pluto in 2016, and which is now some 7 billion kilometres from Earth – far enough to give it a unique view of the heavens around our solar system. On April 2nd/23rd, 2020 the spacecraft was commanded to turn its telescope on two of our nearest stellar neighbours, Proxima Centauri and Wolf 359 (a star doubtless familiar to Star Trek: The Next Generation), some 7.9 light years from Earth, to take pictures of both.

When compared to images of the two stars as seen from Earth, those from New Horizons clearly show how differently the two appear against the background of other stars when seen from different points of observation that are sufficiently far apart.

The New Horizons spacecraft. Credit: NASA

Use of parallax is a common astronomical exercise, used to measure the distance of stars from Earth. However, up until the New Horizons experiment, the average separation between points of observation have been opposite sides in Earth’s orbit around the Sun – or a mere 297,600,000 km apart when averaged out. That’s far enough to allow for an accurate measurements of other stars, but not far enough to show how differently a star might appear from different points in the sky.

It’s fair to say that New Horizons is looking at an alien sky, unlike what we see from Earth.nd that has allowed us to do something that had never been accomplished before—to see the nearest stars visibly displaced on the sky from the positions we see them on Earth.

– Alan Stern, Principal Investigator, New Horizons

For the experiment, the images from New Horizons were compared with images captured by the Las Cumbres Observatory, Panama, operating a remote telescope at Siding Spring Observatory in Australia, and from the Mt. Lemmon Observatory in Arizona, both of which imaged the stars on the same night as New Horizons captured its images, so as to provide a direct comparison.

Witnessing the Birth of Stars

The Rho Ophiuchi cloud complex is a dark nebula of gas and dust that is located 1° south of the star ρ Ophiuchi in the constellation Ophiuchus. Some 460 light-years from Earth, it is one of the closest and active start-forming regions to the Sun.

It’s called a “dark nebula” because the dust cloud is so dense, visible light from stars within it is almost completely obscured. However, astronomers using the Atacama Large Millimetre/submillimetre Array (ALMA) have found something of interest within the cloud.

Two infra-red images of the Rho Ophiuchi nebula showing the IRAS 16293 system within it, as captured by ALMA showing (l) what was thought to be a binary system of stars (A and B), and a closer view of A (r), revealing its own binary nature. The two stars of A re some 54 AU apart. All three stars are surrounded by accretion disks, with the energised dust surrounding the A stars also visible. Credit: Maureira et al

The item in question is IRAS 16293-2422, a system that has a long history of being observed in the infra-red. However, it had been thought the system comprised a binary pairing of protostars, simply referred to as A and B some 700 AU apart. However, the new study has revealed that the star known as A is actually itself a pair of stars, now called A1 and A2. They are both of similar in mass to the Sun – A1 being slightly smaller, and A2 around 1.4 times larger, and each is surrounded by its own accretion disk from which it is drawing material.

These stars and their disks have certain fascinating aspects. The first is that they are only separated by a distance slightly greater to that of Pluto when at aphelion relative to Earth. They also complete an orbit around one another one every 360 terrestrial years. In addition, the accretion disks around A1 and A2 are also unique.

Detailed view of the binary protostar system within IRAS 16293-2422 and with a size comparison to our solar system. The separation between the sources A1 and A2 is roughly the diameter of the Pluto orbit. The size of the disk around A1 (unresolved) is about the diameter of the asteroid belt. The size of the disk around A2 is about the diameter of the Saturn orbit. Image Credit: © MPE

Both disks are extremely active, filaments of matter streaming into the stars at the heart of each, and further filaments of dust flowing into the disks from the nebula. In addition, the disk around A2 disk appears to be oddly inclined compared to the disks around A and the more distant B, suggesting complex interactions may be at play around it. The disk also appears to have parts rotating in opposite directions relative to one another, the first time such a phenomenon has been seen in a protostar accretion disk. It suggests that should planets eventually form around the star, those nearer to it may orbit the opposite direction to those further out.

Organic scans of the disk also detected glycolaldehyde — a simple form of sugar – and Chloromethane, also called methyl chloride, an important biomarker, together with Carbon Sulphide, Isocyanic Acid, Formamide, and Formic Acid. The presence of the organics is important as it shown that the basic building blocks of life can exist within the accretion disks around stars, and so may be available when the remnants of that disk forms planets.

It’s not clear if / when the formation of either star may reach a point of nuclear ignition, or how such an event might affect the other. However, their confirmation provides astronomers with a first-hand opportunity to witness the earliest stage in the process of stellar evolution.

Continue reading “Space Sunday: a touch of astronomy” →

Space Sunday: moving a mole and Planet Nine

Posted on by Inara Pey
InSight’s scoop gently presses against the top of the “mole” of the HP³ experiment, ready to gently push it down into the Martian regolith. Image Credit: NASA/JPL

NASA and its partner, the German Aerospace Centre (DLR) finally have some good news about the Heat Flow and Physical Properties Package, or HP³, carried to Mars by the InSight Lander: they’ve made some progress towards perhaps getting moving again.

As I’ve noted in past Space Sunday articles, the experiment has been a source of consternation for scientists and engineers since InSight arrived on Mars in November 2018. Following the landing, HP³ was one of two experiment packages deployed directly onto the surface of Mars by the lander’s robot arm. One of the key elements of the experiment is the “mole”, a self-propelled device designed to drive its way some 5m into the Martian crust, pulling a tether of sensors behind it to measure the heat coming from the interior of Mars.

After a good start, the probe came to a halt with around 50% of its length embedded in the soil. At first it was thought it had hit solid bedrock preventing further motion; then it was thought that the mole was gaining insufficient traction from the hole walls, on account of the fine grain nature of the material it was trying to move through. That was in February 2019.

The InSight lander was commanded to deploy the HP3 drill system on February 12th, 2019. Credit: NASA/JPL

Since then, scientists and engineers have been trying to figure out what happened, and how to get the mole moving again – because of the delicate nature of the sensor tether, the HP³ experiment couldn’t simply be picked up and moved to another location and the process started over. instead, various attempts were made to try to giving the mole material so it might gain traction.

Most of these revolved around using the scoop at the end of the lander’s robot arm to part-fill / part compress the hole created by the mole, the theory being that loose regolith would gather around the head of the mole and help it regain the necessary fiction to drive itself forward once more. Initially, some small success was had – until the mole abruptly “bounced” almost completely back out of the hole.

Further attempts were made to compress the ground around the hole, but all forward motion remained stalled, leading scientists to believe the mole had struck a layer of “duricrust” – a hard layer formed as a near the surface of soil as result of an accumulation of soluable materials deposited by mineral-bearing waters that later leech / evaporate away. These layers can vary between just a few millimetres to several metres in thickness, and are particularly common to sedimentary rock, which itself has been shown to be common on Mars.

The rub for the InSight mission is that if it is a layer of duricrust beneath the lander, it is impossible to tell just how thick it might be.

This images shows how difficult “pushing” the mole would be. The scoop (upper right) had a very small surface area at the end of the mole with which it could safely make contact, shown circled, without potentially damaging the tether harness. Credit; DLR

Earlier this year it was decided to use the scoop on the robot arm more directly, positioning it over the exposed end of the mole and applying pressure in the hope it could push the mole gently down into the ground in a series of moves that would allow the mole to get to a point were it could resume driving itself into the ground.

However, this approach has not been not without risk. The end of the mole has a “harness” – a connector for the tether, so the scoop has to be precisely positioned and any sort of pressure applied very gently and carefully to avoid any risk of slippage that might result in damage to the tether and / or harness and render its ability to gather data and information from the probe useless.

However, on June 3rd, NASA announced that a series of gentle pushes had resulted in the mole being completely below the surface, and with no apparent damage to the tether or harness. However, whether or not this means the mole is able to proceed under is own self-proplusion is unclear, as NASA noted in their tweet.

In all, the tip of the mole is now some 3m below the Martian surface. That’s deep enough for it to start registering heat flow, but to be effective, the mole still needs to drive itself down the full 5 metres. It is only at this depth that the mole and sensors can correctly start to measure the sub-surface geothermal gradient, and thermal conductivity, the two pieces of information required by scientists to obtain the heat flow from deeper in the planet. By studying the thermal processes in the interior of the planet, scientists can learn a lot about the history of Mars, and how it formed. They may also gain insights into how other rocky bodies formed.

Attempts have yet to be made to see if the mole can move under its own spring-driven propulsion, but for now NASA and DLR are rightly treating the current status of the probe as a victory. The tether harness at the end of the mole is undamaged, so if the mole can resume progress under its own power, there’s not reason why it shouldn’t start recording information.

Continue reading “Space Sunday: moving a mole and Planet Nine” →

Space Sunday: how to fly your Dragon

Posted on by Inara Pey
The International Space Station imaged from 200 metres by the docking systems camera looking out of the forward hatch window of SpaceX Crew Dragon Endeavour. Credit: SpaceX / NASA

On Saturday, May 30th, 2020 the United States successfully launched astronauts into orbit from American soil for the first time since July 8th, 2011. It came after an initial attempt on May 27th, 2020 had to be scrubbed (called off) due to adverse weather conditions putting the launch vehicle at risk of a possible electrical strike.

As I noted in my previous Space Sunday piece, the primary goal of the mission is to confirm the SpaceX Crew Dragon vehicle is ready to commence operations ferrying crew to and from the International Space Station. Intended to fly up to four crew at a time on such missions, for this final test flight, Crew Dragon lifted-off with only two crew aboard: NASA veterans Robert L. Behnken (flight pilot) and Douglas G. Hurley (commander).

NASA astronauts Bob Behnken (l) and Doug Hurley, photographed at the top elevator station at Launch Complex 39A, Kennedy Space Centre, at a dress rehearsal for the Crew Dragon Demo-2 flight, May 24th, 2020. Credit: SpaceX

Weather was also a concern in the run-up to the May 30th launch, with NASA putting a chance of lift-off at 50/50 through to less than an hour ahead of the launch time. However, after a burst of rain in the area of Kennedy Space Centre as the Falcon 9 launch vehicle was being prepared for lift-off, the weather situation both around the Florida Cape and downrange of the launch site and along the track of the vehicle’s line of ascent, cleared sufficiently for the launch to go ahead.

The entire launch, from the astronauts suit-up in the crew room at Kennedy Space Centre, through lift-off, ascent to orbit, on-orbit operations and the rendezvous and docking with the International Space Station some 19 hours after launch, was covered entirely live through NASA TV and SpaceX on You Tube and other channels. This coverage made it one of the mos-watched launches of a space vehicle despite the limitations of travel in place due to the SARS-CoV-2 pandemic, with 1.5 million people watching the SpaceX relay of the NASA feed alone.

Thursday, May 21st, 2020: The Falcon 9 / Crew Dragon vehicle bearing the NASA worm and meatball logos, rolls out of the SpaceX vehicle processing building en route to pad 39A

Following their arrival at the launch pad some 2+ hours ahead of the the launch, the astronauts – known as “the Dads” to the SpaceX team – travelled to the top of the launch tower prior to ingressing into the Crew Dragon vehicle and performing a series of pre-flight checks both before and after the crew hatch was closed-out by the fight support crew.

At around an hour prior to launch and with the flight support crew clear of the tower, the access arm was rotated clear and fuelling of the Falcon 9’s first and second stage tanks commenced as the weather clearance was given. Unlike Apollo and the shuttle, the SpaceX vehicles go through fuelling as a last stage of ground operations to minimise the amount of fuel venting / topping-up that is required as the super-cold liquid propellants start to slowly warm despite insulation and cooling.

Ahead of the launch, the ISS passed over Kennedy Space Centre and this photograph was taken. Centre top is the massive Vehicle Assembly Building where the SLS will be assembled for launch and the former Orbiter Processing Buildings, one of which is now used by Boeing for the Starliner crew vehicle and another by the Orion MPCV; The crawler / transporter track runs from the VAB toward the coast, splitting so one leg runs to the right and Pad 39B, which will host the SLS, while the second runs down to Pad 39A where the white SpaceX vehicle assembly building can be seen, with the Falcon 9 on the pad. Credit: NASA

A crucial aspect of the Demo-2 launch was that orbital mechanics demanded the vehicle had to lift-off precisely on time – there could be no “holds” that delayed it beyond the appointed lift-off time. Were launch to be delayed, even by a few minutes, the Crew Dragon would reach orbit at the wrong point related to the ISS, and so and rendezvous would be much harder, if not impossible, given what needed to be achieved in the flight ahead of reaching the space station.

So, at 19:22:45 UTC, precisely on schedule, the nine motors of the Falcon 9’s first stage igniting, lifting the black-and-white rocket and capsule vehicle smoothly off the pad. This marked a further first for the mission: not only was it the first US crewed mission into space undertaken from US soil bult and operated by a private company, the entire launch process was run by SpaceX and not by NASA’s Mission Operations Control Room (MOCR – or “moe-kerr”) at the Johnson Space Centre (JSC), although the latter were obviously looking over SpaceX’s shoulder and monitoring things, with the ISS Fly Operations Centre fully “in the loop”.

A Dragon rises with its riders as the Falcon 9 clears the tower at LC-39A, May 30th, 2020. Credit: NASA live stream

Ascent to orbit lasted some 8 minutes – although to all those watching, it probably seemed a lot quicker. Powering the vehicle through the denser part of the atmosphere, the Falcon’s first stage reached MECO (main engine cut-off) just over 2 minutes after launch. Separating, this continued along a ballistic trajectory, flicking itself around to deploy vanes to help with its descent back though the atmosphere so it might make a landing on the autonomous drone ship Of Course I Still Love You.

Camera footage from the first stage, transmitted as the Falcon’s second stage continued to boost the Crew Dragon vehicle to orbit, showed it orienting itself using its attitude thrusters, prior to three of the Raptor engines firing to slow it down and cushion it as it dropped back into denser atmosphere. From here, it dropped smoothly back towards the drone ship, the deployed vanes holding it upright. Unfortunately, video footage was lost prior to touch-down, but moments later, the feed resumed, showing the stage sitting on the ship’s deck as high above, the Falcon’s second stage reached SECO – Second (Stage) Engine Cut-off, and shortly after, the Dragon separated from it.

Timing in the flight meant that the Falcon 9 first stage successfully landed on the autonomous drone ship Of Course I Still Love You (l) at almost the same time as SECO was reached by the rocket’s upper stage, followed a couple of minutes later by Crew Dragon successfully separating from the second stage (r). Credit: SpaceX

Continue reading “Space Sunday: how to fly your Dragon” →

Space Sunday: launches, names, and departures

Posted on by Inara Pey
A remarkable shot of the SpaceX Demo-2 Falcon 9 and Crew Dragon, due to launch on May 27th, 2020, on the pad at Launch Complex 39A, Kennedy Space Centre. It was taken at an altitude of some 650 km above the surface of the Earth by the Maxar Worldview-3 satellite. Credit: Maxar Technologies (formerly DigitalGlobe)

If all goes according to plan, the United States will make its first crewed launch from its home soil since the space shuttle programme drew to a close in 2011.

On May 27th, 2020, shrouded in additional safety protocols to protect crews from the SARS-CoV-2 virus, a SpaceX Falcon 9 booster should lift off from the company’s launched pad – leased from NASA – at Launch Complex 39A, Kennedy Space Centre, Florida. Aboard the Crew Dragon vehicle at the top of the rocket will be NASA veterans Robert L. Behnken and Douglas G. Hurley, who will be heading to the International Space Station (ISS).

The primary goal of the mission – referred to as Dmeo-2 by SpaceX and SpX DM-2by NASA – is to confirm the SpaceX Crew Dragon vehicle is ready to commence operations ferrying crew to and from the ISS. To this end, NASA has contracted SpaceX to provide the agency with 6 Crew Dragon launches to carry four astronauts at a time to and from the ISS; the vehicle is actually capable of carrying up to seven per flight, but NASA will use the additional capacity for light cargo and equipment bound for the ISS.

NASA astronauts Bob Behnken and Doug Hurley discuss the upcoming Demo-2 commercial crew test flight after arriving at the Kennedy Space Centre May 20. Credit: NASA/Bill Ingalls

In addition to flying crews on behalf of NASA, SpaceX has also been contracted by Axiom Space to fly one Axiom professional astronaut and three private astronauts at a time to the ISS for periods of around 10 days at a cost of US $55 a seat. However, these private astronauts are not necessarily space tourists: Axiom is committed to developing the world’s first fully commercial space station.

As a part of this, the company entered into an agreement with NASA to dock three of its own space station modules to the ISS to kick-start their station development, with the first module potentially being launched in 2024. These modules will be used to host experiments and research by Axiom and their partners; following the retirement of the ISS (around 2028), Axiom plan to launch their own power and thermal module, airlock system and habitation module to replace the ISS facilities.

Not that SpaceX and the Crew Dragon won’t be involved in space tourism; the company has also partnered with Space Adventures to provide sets to fly up to four space tourists at is time on orbital flights lasting between three and five days. These will have an apogee three times that of the ISS and higher than the Earth orbital altitude record set by Gemini 11 in 1966.

Astronauts Douglas G. Hurley (l) and Robert L. Behnken in their futuristic (and vacuum-capable) space suits designed by SpaceX, posing alongside their Tesla (what else?) crew vehicle during a full launch dress-rehearsal on Saturday, May 23rd, 2020

In the meantime , this first crewed flight with see Behnken  and Hurley rendezvous with the ISS the day after launch (May 28th if the launch goes ahead as planned). The docking will be carried our autonomously – as will the majority of the flight, although the crew can fly the vehicle manually at any time, including the docking. Once at the ISS, the crew and vehicle will remain there for around four weeks, before making a return to Earth.

Hurley and Behnken arrived at Kennedy Space Centre on May 20th, ahead of the final flight readiness review (FRR) for the mission, which took place on May 22nd. This cleared the mission for its planned launch after an extensive review of all the Crew Dragon’s systems, notably its parachute system, which has been a point of concern for NASA after the parachutes had to go through a complete redesign and a rapid series of tests in the lead-up the the flight.

Following the FRR, SpaceX proceeded with a standard static-fire test of the Falcon 9’s first stage engines in readiness for launch, which the booster completed successfully. On Saturday, May 23rd, crew and vehicle went through full launch dress rehearsal. This will be followed by a final series of tests and checks on both the booster and Crew Dragon vehicle in the lead up to the launch, which is currently scheduled for 16:33 EDT on May 27th. It will come just over a year since Crew Dragon made its first (uncrewed) flight to the ISS in May 2019.

Crew Dragon comprises the main (potentially re-usable) capsule and a single-use service module that provides propulsion and power. Credit: Archipeppe68

Crew Dragon is intended to be semi-reusable, with each capsule potentially capable of being re-flown after refurbishment following a flight. However, the vehicles used by NASA will only be flown once each. It has been said this is due in part to a decision not to use Dragon’s propulsive landing capabilities with NASA missions, but to instead make ocean splashdowns when returning crews to Earth, exposing the capsules to sea water contamination. Even so, it is estimated the per-seat cost for launching NASA astronauts on Crew Dragon is around 40% less than the cost of a seat on the Boeing Starliner.

Continue reading “Space Sunday: launches, names, and departures” →

Space Sunday: to land on Europa

Posted on by Inara Pey
An artist’s impression of the Europa Lander. Credit: NASA

Of all the planets and moons in the solar system, the two that – next to Earth – are likely to be homes to oceans of liquid water are Jupiter’s moon Europa, and Saturn’s Moon Enceladus. The latter, as I’ve noted in this column, has visible evidence of geysers venting water vapour around its southern polar regions, while in November 2019, the the W.M. Keck Observatory indicated they had directly detected water vapour around Europa (see here for more) – evidence that has since been added to through further study of the data gathered by NASA’s Galileo mission that ended in 2003.

Given their distance from the Sun, both of these moons are covered in shell of icy material  that is believed to encase a liquid water ocean, likely heated from within by hydrothermal vents, themselves the result of both moons being “flexed” by the gravitational influence of their parent planets and the other large moons orbiting them. And where there is water, heat and a source of energy for sustenance, there is a possibility that life may also be present – which makes both Enceladus and Europa potential destinations in the search for life beyond our own world; and of the two, Europa is somewhat “easier” to reach.

A high resolution image of Europa’s chaotic surface taken by the Galileo mission. It shows terrain where blocks of material have shifted, rotated, tilted and refrozen. Credit: NASA/JPL

To this end, and again as has been written about in this column, in 2024 NASA intends to send the Europa Clipper to the Jovian system, placing it in a orbit around Jupiter that will allow it to make repeated fly-bys of Europa, joining the European Space Agency’s Jupiter Icy Moons Explorer allowing it so study the moon in detail, and characterise its surface and any ocean that might lay beneath.

However, to have a real chance of detecting any evidence of microbial life on Europa, scientists argue that a landing there is required, and as planetary scientist Conor A Nixon reminded me via Tweeter, a proposal to put a lander on the surface of Europa has been in development for over two years – although it has yet to reach the point of actually being funded. Were it to go ahead, it would – amongst other things – be the heaviest robot mission launched from Earth; so heavy, it would require either the Falcon Heavy or NASA’s massive Space Launch System (SLS) to throw it on its way to Jupiter – with the SLS being the preferred vehicle, as it would allow the mission to reach Jupiter after just a single gravity assist from Earth, shortening the flight time.

The proposed Europa Lander mission outline, as it stood in 2018, and reviewed in 2019. Credit: NASA

The primary objectives of the mission would be to search for subsurface biosignatures; to characterise the surface and subsurface properties at the scale of the lander to support future exploration of Europa and determine the proximity of liquid water and recently erupted material near the lander’s location; and assess the habitability of Europa via in situ techniques uniquely available to a landed mission. Under current plans, last revised in 2019, the mission  – outside of this launcher – will comprise five core elements:

  • The Europa Lander: a battery-powered vehicle intended to operate on the surface of Europa for 22 terrestrial days, and carrying a suite of around 14 scientific instruments / experiments.
  • The Descent Stage (DS): to reduce the risk of contaminating / damaging the lander’s touch-down point, it will be winched down to the surface by a “sky crane” vehicle similar to the one used to put the Curiosity lander on Mars and will be used with the Perseverance rover in February 2021. Once the sky crane has done its job, the sky crane will boost itself into an orbit where it will eventually burn-up in Jupiter’s upper atmosphere.
    • Together, the lander and the DS form what NASA call the Powered Descent Vehicle (PDV).
  • The De-Orbit Stage (DOS): a propulsion unit intended to slow the PDV into a decent to the surface of Europa.
    • When combined the DOS and PDV form the De-Orbit Vehicle (DOV).
  • This assembly is carried to Jupiter within the carrier stage, comprising two parts:
    • The carrier vehicle, which provides communications, power and flight management hardware and software.
    • A protective bio-barrier dome designed to protect PDV from the risk of contamination / damage during the 5-year trip to Jupiter.
The Europa Lander’s component element. Credit: NASA

Continue reading “Space Sunday: to land on Europa” →