Space Sunday: hearing Mars, looking at Bennu and roving the Moon

One of InSight’s 2.2 metre (7-ft) wide solar panels was imaged by the lander’s Instrument Deployment Camera fixed to the elbow of its robotic arm. Credit: NASA/JPL

It’s always a remarkable time when a new mission arrives on or around another planet in our solar system, so forgive me if I once again kick-off a Space Sunday with NASA’s Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) lander, which touched down on Mars just 10 days ago.

Over the course of the last several days, NASA has been putting the lander’s 1.8 metre (6 ft) long robot arm through its paces in readiness for operations to commence. The arm has multiple functions to perform, the most important of which is to place two major science experiments on the surface of Mars. The arm is also home to one of the two camera systems on the Lander.

InSight’s deck partially imaged be the IDC on the lander’s robot arm. Credit: NASA/JPL; annotations: Inara Pey

Very similar to the Navcam systems used by both Opportunity and Curiosity, the camera is called the Instrument Deployment Camera (IDC). It is mounted above the arm’s “elbow” and has a 45-degree field of view. As well as offering a first-hand view of everything the robot arm is doing, IDC can provide colour, panoramic views of the terrain surrounding the landing site.

The arm hasn’t as yet been fully deployed, but in being put through its paces, it has allowed the IDC to obtain some tantalising views of both the lander and its surroundings.

Left: a view of the ground scoop on the robot arm, again seen with the grapple stowed. Note this image was captured with the protective dust cover still in place over the camera lens. Right: a view of InSight’s deck. The copper-coloured hexagonal object is the protective cover for the seismometer, and the grey dome behind it is the wind and thermal shield which will be placed over the seismometer after its deployed. The black cylinder on the left is the heat probe, which will drill up to 5 metres into the Martian surface. Image: NASA/JPL

Some powering-up of science systems has also occurred, notably Auxiliary Payload Sensor Systems (APSS) suite. The air pressure sensors immediately started recording changes in air pressure across the lander’s deck indicative of a wind passing over InSight at around 5 to 7 metres a second (10-15mph). However, the biggest surprise can from the seismometer designed to listen to the interior of Mars.

As this was tested, it started recording a low-frequency vibration in time with the wind recordings from APSS. These proved to be the wind blowing over the twin 2.2-metre circular solar panels, moving their segments slightly, causing the vibrations, which created a sound at the very edge of human hearing. NASA later issued recordings of the sounds, some of which were adjusted in frequency to allow humans to more naturally “hear” the Martian wind.

The InSight lander acts like a giant ear. The solar panels on the lander’s sides respond to pressure fluctuations of the wind. It’s like InSight is cupping its ears and hearing the Mars wind beating on it.

– Tom Pike, InSight science team member, Imperial College London

Once on the surface of Mars and beneath its protective dome, the seismometer will no longer be able to hear the wind – but it will hear the sound of whatever might be happening deep within Mars. So this is likely to be the first of many remarkable results from this mission.

To Touch an Asteroid

NASA’s OSIRIS-REx (standing for Origins, Spectral Interpretation, Resource Identification, Security – Regolith Explorer), launched in September 2016, has arrived at its science destination, the near-Earth asteroid Bennu, after a journey of two billion kilometres.  It will soon start a detailed survey of the asteroid that will last around  year.

Bennu as seen by OSIRIS-REx. Credit: NASA

Bennu, which is approximately 492 m (1,614 ft) in diameter, is classified as a near-Earth object (NEO), meaning it occupies an orbit around the Sun that periodically crosses the orbit of Earth. Current orbital predictions suggest it might collide with Earth towards the end of the 22nd Century.

To this end, OSIRIS-REx will analyse the thermal absorption and emissions of the asteroid and how they affect its orbit. This data should help scientists to more accurately calculate where and when Bennu’s orbit will intersect Earth’s, and thus determine the likelihood of any collision. It could also be used to better predict the orbits of other near-Earth asteroids.

Bennu is primarily comprised of carbonaceous material, a key element in organic molecules necessary for life, as well as being representative of matter from before the formation of Earth. Organic molecules, such as amino acids, have previously been found in meteorite and comet samples, indicating that some ingredients necessary for life can be naturally synthesized in outer space. So, by gaining samples of Bennu for analysis, we could answer many questions on how life may have arisen in our solar system – and OSIRIS-REx will attempt to do just that.

Towards the end of the primary mission, OSIRIS-REx will be instructed to slowly close on a pre-selected location on the asteroid, allowing a “touch and go” sampling arm make contact with the surface for around 5 seconds. During that moment, a burst of nitrogen gas will be fired, hopefully dislodging dust and rock fragments, which can be caught by the sampling mechanism. Up to three such sample “hops” will be made in the hope that OSIRIS-REx will gather between 60 and 2000 grams (2–70 ounces) of material. Then, as its departure window opens in March 2021, OSIRIS-REx will attempt a 30-month voyage back to Earth to deliver the samples for study here.

Continue reading “Space Sunday: hearing Mars, looking at Bennu and roving the Moon”

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Space Sunday: InSight, MarCO and privately to the Moon

A simulation of InSight touching down on Mars using its 16 rocket motors. Credit: NASA

On Monday, November 26th, 2018, the latest in a series of NASA missions, the InSight lander – built with international cooperation -, arrived on the surface of Mars.

As noted in my previous Space Sunday report, confirmation that InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) had safely arrived could only be received by mission control at NASA’s Jet Propulsion Laboratory (JPL) after the team there had endured the “seven minutes of terror”, more officially known as the Entry, Descent and Landing (EDL) phase of its journey, the time when the vehicle would enter Mars’ atmosphere and hopefully make a reasonably soft-landing on the planet’s surface.

While undeniably tense, when it came to it – and watched live via social media,  and assorted web broadcast channels put out by NASA – EDL was completed flawlessly. After separating from is cruise element around 7 minutes prior to EDL, InSight, protected by its heat shield and aeroshell, entered the upper reaches of the Martian atmosphere almost precisely on schedule, where over a 4-minute period, the frictional heat created by is passage helped decelerate it from an initial entry velocity of 19,800 km/h (12,300 mph) to 1,400 km/h (860 mph). At this point, telemetry once again being relayed, the supersonic braking parachute was been deployed.

After this things moved quickly: the heat shield was jettisoned from under the lander, which itself dropped free of the parachute and conical aeroshell, using its 16 rocket motors to achieve a “soft” landing on the surface of Mars – travelling at just 8 km/h (5 mph). A video compressing the seven minutes into just over a minute and a half captures the landing – and the joy at mission control (not the celebratory handshake at 1:19!).

It had been anticipated that the first “official” confirmation that InSight had arrived safely would be a “beep” sent directly to Earth from the lander’s X-band radio – and this might be followed a few minutes later by a photograph taken by the lander. As it turned out, and thanks to two tiny CubeSats – of which  more in a moment – it was the photo that arrived first. Grainy and indistinct due to it being taken by a camera still with its protected lens cap in place (itself splattered with dust), it shows a rocky surface and a tightly curved horizon – caused by the camera still being in its stowed configuration.

Side-by-side: (l) the first image returned by InSight using the lander-mounted, Instrument Context Camera (ICC), still with its dust cap in place – note the lander’s leg in the lower right corner. (r) a photo captured by the robot-arm mounted Instrument Deployment Camera (IDC), also taken with the lens cap in place, as the arm is exercised on November 30th, 2018. Credit: NASA/JPL

Initially after landing, InSight was operating on battery power whilst awaiting the dust to settle out of the atmosphere so the two circular solar panels could be deployed. This occurred some 30 minutes after touchdown, with the panels proving so efficient that . So efficient are these panels that during their Martian Sol of operation, they set a new record for power generation: 4,588 watt-hours – well over the 2,806 watt-hours generated in a single Sol by the “nuclear powered” Curiosity.

The efficiency of InSight’s solar arrays will deteriorate over time – the result of general wear-and-tear and the influence of dust that will inevitably accumulate on them – but the power levels have been more than enough for the lander to start flexing its muscles – including testing its robot arm, which is essential to it being able to place key experiments on the surface on Mars.

A computer simulation of InSight deploying its solar arrays. Credit: NASA

It is going to be early spring 2019 before InSight is fully involved in its science mission. There are a lot of equipment check-outs and calibration test to be undertaken, as well as the surface deployment of key instruments. However, there have been some external concerns raised over how well InSight will fulfil its science objectives. As data started coming back from the lander, it was noted that it had touched down in a shallow impact crater, almost completely filled by sand and dust (such craters being known as “hollows” on Mars), which has given InSight a 4-degree tilt.

Overall, the lander can in theory operate with up to a 15-dgree cant (the result of one of this three landing legs coming down on a boulder, for example), but here is a worry about how the tilt may impact placing the Seismic Experiment for Interior Structure (SEIS) and HP3, the Heat Flow and Physical Properties Package, on the surface of Mars, and how the material filling the hollow might affect the operation of HP3’s “mole”, which is designed to burrow into subsurface rock and measure the heat flow from the centre of the planet.

Computer simulation of Insight Placing the Seismic Experiment for Interior Structure (SEIS) experiment and its dust cover on the surface of Mars. Credit: NASA/JPL

Nevertheless the mission team remain in a positive mood and are delighted with both the landing and the first few days of operations.

We couldn’t be happier. There are no landing pads or runways on Mars, so coming down in an area that is basically a large sandbox without any large rocks should make instrument deployment easier and provide a great place for our mole to start burrowing.

– InSight project manager Tom Hoffman

Further examination of the lander’s surroundings will be made once the dust covers have been ejected from the on-board cameras, something that should happen in the next few days. This work will include a careful study of the ground to determine the best placement for SEIS and HP3, as well as a general surveying of the location, which in the initial images, appears a lot less rock-strewn than other locations visited by landers and rovers.

We are looking forward to higher-definition pictures to confirm this preliminary assessment. If these few images—with resolution-reducing dust covers on—are accurate, it bodes well for both instrument deployment.

– Bruce Banerdt, InSight principal investigator

I’ll have more on InSight as the mission develops.

Continue reading “Space Sunday: InSight, MarCO and privately to the Moon”

Space Sunday: seven minutes of terror and a round-up

Virgin Orbit
An artist’s impression of InSight on Mars. Credit: ETH Zurich

Mars is actually the most-studied planet in the solar system after Earth. In the last two decades alone, it has been under constant observation and study, yet we know very little about the Red Planet’s interior.

That should change from Monday, November 26th, 2018, when NASA’s latest mission to Mars, the Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) lander touches down on Elysium Planitia.

The aim of the mission is to carry out a detailed examination of the Red Planet’s interior – its crust, mantle and core. Doing so can answer key questions about the early formation of the rocky planets in our inner solar system – Mercury, Venus, Earth, and Mars – more than 4 billion years ago. In addition, the data gathered may also help us to understand how rocky exoplanets orbiting other stars in our galaxy may have formed.

An artist’s impression of InSight on Mars, showing the SEIS package deployed. Credit: NASA / JPL

I’ve covered some of the more unique aspects of the mission in previous Space Sunday articles (see Insight on InSight, May 2018 and Mars Roundup, October 29th), including the use of two unique surface instruments, the Seismic Experiment for Interior Structure (SEIS) and HP3, the Heat Flow and Physical Properties Package to probe the planet’s interior. However, in order for the lander to use these, and its other instruments, it must conclude its 6-month journey to Mars with the Entry, Descent and Lander (EDL) phase – or as NASA mission engineers are calling it, 7 minutes of terror.

So-called since the 2012 landing of the Curiosity rover on Mars, it is known as such because by the time mission control receives the initial signals indicating the start of EDL, the Lander will be on the surface of Mars – in one piece or otherwise. These crucial seven minutes comprise (in the anticipated Earth Receive Time, when the signals are expected to reach NASA’s Jet Propulsion Laboratory):

  • 19:47 GMT: encased in its aeroshell, InSight will enter the upper reaches of Mars’ discernible atmosphere 114 km (77 mi) above the surface of planet at 19,800 km/h (12,300 mph) at a critical 12-degree angle of attack. Any less than this, and it could bounce back into space, any greater and the heat generated by atmospheric entry could overwhelm the heat protection (designed to withstand temperature up to 1,500oC / 2,700oF, which is reached  2 minutes into the entry sequence), and burn-up the lander.
  • 19:51 GMT: having been slowed to 1,400 km/h (860 mph) and at an altitude of 11 km (7 mi), the primary parachute is deployed. 15 seconds after this, the lower heat shield is jettisoned, and 10 second after that, the three landing legs are deployed.
  • 19:52 GMT: ground sensing radar activates to measure the distance to the ground.
  • 19:53:25 GMT: the lander separates from it aeroshell and parachute and the landing motors start firing as the lander orients itself for touchdown.
  • 19:53:47 GMT: the motors reduce velocity from 27 km/h to 8 km/h (17 mph to 5 mph).
  • 19:54 GMT: InSight touches down, with the motors immediately shutting down to avoid “bouncing” or toppling.
Virgin Orbit
An artist’s impression of InSight touching-down on Mars under propulsive power. Credit: NASA

Depending on how systems check-out, the first image from InSight could be received by mission control about 8-10 minutes after landing – although equally, it could be received any time in the first 24 hours after landing. The Mars Odyssey orbiter should overfly the landing area at around 01:30 GMT on November 27th, and will hopefully be able to image InSight on the surface of Mars with its large, circular solar panels fully deployed – these will initially remain in their stowed  configuration for around 20 minutes following landing to allow the dust thrown up by the lander’s motors to disperse and settle so that it doesn’t interfere with their operation.

Once settled on Mars, the primary mission, designed to run for a full Martian year, will commence – although it will be one that could take time to unfold.

InSight is kind of a laid-back, slow-motion mission. It’s going to take us probably two to three months, at least, to get our instruments down, and it could be early next spring before our principal instruments started returning data.

– InSight principal investigator Bruce Banerdt

As well as direct transmissions during EDL, NASA hopes to get real-time telemetry of the landing from a pair of cubesats, called Mars Cube One (MarCO), that launched as secondary payloads with InSight in May, and which will fly past Mars during the landing.

For those who wish to follow it, the InSight landing will be broadcast on a number of NASA on-line resources available.

Continue reading “Space Sunday: seven minutes of terror and a round-up”

Space Sunday: exoplanets ‘Oumuamua and rockets

An artist’s impression of the surface of Barnard’s Star b. Credit ESO-M. Kornmesser. Credit ESO-M. Kornmesser

Another of our Sun’s closest neighbours has been found to be home to a “super-Earth” scale planet.

Barnard’s Star, named after American astronomer Edward Emerson Barnard, is a low-mass M-class red dwarf star. As I’ve noted in previous discussions of exoplanets, red dwarf stars are the most common type of star in our galaxy, believed to account for around 70% of all stars. They can be quite volatile in nature and prone stellar flares, meaning any planets in close proximity to them are unlikely to be very habitable.

But Barnard’s Star is somewhat unusual; while it is estimated to be between two and three times older than the Sun, it has a relatively low level of activity. It also has the fastest radial (side-to-side) motion of any visible star in the night sky – something that might indicate the presence of a large planet orbiting it, causing it to wobble in its spin.

Over the years, astronomer have attempted to use the star’s radial motion to try to establish if it is the result of a planet, and in 2015, instruments used by the European Southern Observatory and the Keck Observatory suggested there could be a very large planet with an orbital period of about 230 days.

More recently, the Red Dots and CARMENES campaigns, which were responsible for the discovery of a planet orbiting our nearest stellar neighbour, Proxima B (see here for more), reviewed the data gathered from multiple sources that have studied Barnard’s Star in an attempt to ascertain whether there is one or more planets orbiting Barnard’s Star.

An artist’s impression of Barnard’s Star planet under the orange tinted light from the star. Credit: IEEC/Science-Wave – Guillem Ramisa

For the analysis we used observations from seven different instruments, spanning 20 years, making this one of the largest and most extensive datasets ever used for precise radial velocity studies. The combination of all data led to a total of 771 measurements.

– Ignasi Ribas, director of the Monstec Astronomical Observatory, and study lead

The results of this work appear to confirm that there is a planet – referred to as Barnard’s Star b – is orbiting the star roughly one every 233 terrestrial days. It has a mass of at least 3.2 times that of Earth, putting it if the category of either a “super-Earth” or a “mini-Neptune”. It is some 0.4 AU (0.4 times the distance between the Earth and the Sun) from its parent.

Because of Barnard’s Star low mass and brightness, the planet only receives about 2% of the energy that the Earth receives from the Sun. This puts it at, or beyond the star’s frost line, where volatile compounds like water, carbon dioxide, ammonia and methane condense into solid ice. As a result, the planet likely has a surface temperature in the region of -170oC, making it inhospitable to life as we know it – although if the planet has an atmosphere, its surface temperature could be higher.

This is the first time an exoplanet has been discovered using the radial velocity method. The most common method of detection is the transit method, monitoring the period dimming of a star’s brightness as seen from Earth to determine whether a planet might be orbiting it, but such is Barnard’s Star’s dimness, this has never really been and option.

Further observations are required to completely confirm the planet’s presence, but those involved in the study – including ESO – have a high degree of confidence it will be confirmed, and observations by a number of observatories around the globe are already underway.

After a very careful analysis, we are over 99 per cent confident that the planet is there, since this is the model that best fits our observations. However, we must remain cautious and collect more data to nail the case in the future … we’ll continue to observe this fast-moving star to exclude possible, but improbable, natural variations of the stellar brightness which could masquerade as a planet.

– Ignasi Ribas

Such is the proximity of Barnard’s Star to Earth, the new planet is potentially an excellent candidate for direct imaging using the next-generation instruments both on the ground and in space – such as with NASA’s James Webb Space Telescope (JWST), scheduled for launch in 2021) or Wide Field InfraRed Survey Telescope (WFIRST), which if not threatened with further cancellation, should be launched in the mid-2020s, and the European Space Agency’s Gaia mission.

‘Oumuamua Update

In my previous Space Sunday article, I wrote about our interstellar visitor, ‘Oumuamua (officially 1I/2017 U1), which was observed passing around the Sun a year ago, and the (unlikely) potential it is some form of extra-terrestrial probe.

On November 14th, 2018, NASA issued an update on the most recent findings from data obtained on the cigar-shaped object by the Spitzer infra-red telescope.

An artist’s impression of 1I/2017 U1 (or `Oumuamua), which was first seen by the Pan-STARRS 1 telescope in Hawaii on October 19th, 2017, and subsequently studied by a number of telescopes around the world, including the VLT of the European Southern Observatory (ESO) Credit: ESO / M. Kornmesser

The new report, released via NASA’s Jet Propulsion Laboratory, indicates ‘Oumuamua is off-gassing volatiles, something those proposing the alien probe idea thought to be unlikely. This off-gassing likely imparted the odd tumbling motion exhibited by ‘Oumuamua . Spitzer’s observations also confirmed that the object is highly reflective – around 10 times more reflective than the comets that reside in our solar system—a surprising result, according to the paper’s authors.

Comets orbiting the Sun spend a good deal of their time gathering dust suspended in the interplanetary medium, covering them in a layer of “dirt”. As they approach the Sun, they undergo heating, causing volatiles  – often frozen water – to start venting, “cleaning” parts of the comet’s surface and raising its reflectivity. As ‘Oumuamua, has been in the depths of interstellar space for millennia and far from any star system that could contain enough dust and material to refresh its surface, it is possible that the off-gassing confirmed by Spitzer exposed far more of its underlying ice. This, coupled with some of the icy volatiles it vented falling back onto its surface (again as can happen with solar system comets) may have resulted in the object’s higher than expected albedo.

Taken with other observations of ‘Oumuamua, the Spitzer data tends to further discount the idea that it is of artificial origin.

Continue reading “Space Sunday: exoplanets ‘Oumuamua and rockets”

Space Sunday: ‘Oumuamua, BFS and Tianhe-1

An artist’s impression of 1I/2017 U1 (or `Oumuamua), which was first seen by the Pan-STARRS 1 telescope in Hawaii on October 19th, 2017, and subsequently studied by a number of telescopes around the wrold, including the VLT of the European Southern Observatory (ESO) Credit: ESO / M. Kornmesser

On October 19th, 2017, the Panoramic Survey Telescope and Rapid Response System-1 (Pan-STARRS-1) in Hawaii announced the first-ever detection of an interstellar asteroid, named 1I/2017 U1 (aka. ‘Oumuamua).

In the months that followed, multiple additional observations were conducted that allowed astronomers to get a better idea of its size and shape, revealing it to be strangely cigar-shaped, roughly 400 metres (1312 ft) in length and approximately 40-50 metres (130-162.5 ft) in height and width, tumbling through space. These observations also showed it may be composed of dense metal-rich rock, and that it had the characteristics of both a comet and an asteroid.

However, the report on ‘Oumuamua (roughly translated as “scout”, ou being Hawaiian for “reach out for” and mua meaning “first, in advance of” – which is repeated for emphasis) that captured public imagination is the idea that the object may have been an interstellar probe.

At the heart of this idea is the fact that ‘Oumuamua accelerated away from the Sun faster than would have been the case of it receiving a “gravity assist” in swinging around our star. Initially, it was suggested that the additional acceleration was the result of the off-gassing of volatiles  – frozen water, etc., that had been heated during ‘Oumuamua’s close swing around the Sun. However, no such off-gassing had been observed when the object was closer to the Sun, which would have been expected.

‘Oumuamua’s passage around the Sun in 2017. Credit: Tom Ruen, via wikipedia

In June 2018, an alternative explanation for the acceleration was posited: that it was the result of solar pressure being exerted on the object.

However, at the end of October 2018, Shmuel Bialy, a post-doctoral researcher at the CfA’s Institute for Theory and Computation (ITC) and Prof. Abraham Loeb, the Frank B. Baird Jr. Professor of Science at Harvard University, went one stage further. They proposed that while ‘Oumuamua might well be natural in origin – it could also be the object is in fact an alien probe, intentionally sent to our solar system and which uses a light sail (or what we’d call a solar sail were it to be used with a probe sent from Earth to explore out solar system) for propulsion.

Currently there is an unexplained phenomena, namely, the excess acceleration of ‘Oumuamua, which we show may be explained by the force of radiation pressure from the Sun. We explain the excess acceleration of `Oumuamua away from the Sun as the result of the force that the Sunlight exerts on its surface. For this force to explain measured excess acceleration, the object needs to be extremely thin, of order a fraction of a millimetre in thickness but tens of meters in size. This makes the object lightweight for its surface area and allows it to act as a light-sail. Its origin could be either natural (in the interstellar medium or proto-planetary disks) or artificial (as a probe sent for a reconnaissance mission into the inner region of the Solar System).

– E-mail from Baily and Loeb on their paper concerning ‘Oumuamua

Their views were circulated to various news outlets via e-mail and cause something of a stir in the first week or so of November.

Loeb has actually been an advocate of ‘Oumuamua being of intelligent origin since it was first discovered. He was one of the first to call for radio telescopes to listen to it across a range of frequencies for any signs of transmissions from it. When the SETI Institute‘s Allen Telescope Array did so without success, he pushed for the Green Bank Telescope in West Virginia to listen for radio emissions – which it did for a 6-day period December 2017, again without success

As no signals were found to be emanating from the object, rather than drop the idea of it being artificial, Loeb has put forward the ideas that it has either malfunctioned, or it is active, and we simply can’t detect the fact that it is. He’s even suggested that given Pan-STARS only managed to spot the object after it has passed perihelion, could mean that it is only “one of many” such probes sent our way, and we’ve missed the others.

Bialy has been a little more cautious with things, pointing out the paper is “high speculative”. But the fact is, the paper does come across more of an attempt to substantiate a belief (that ‘Oumuamua is of artificial origin) than anything else, and in doing so, it does ignore certain data and makes some sweeping assumptions.

For example, the paper tends to dismiss the idea that ‘Oumuamua’s unexpected acceleration was consistent with a push from solar radiation pressure. However, Michele Bannister, a planetary astronomer from New Zealand and one of many to push back against the “ET probe” idea via Twitter, used a graphic that shows the acceleration exhibited by ‘Oumuamua’s is entirely in keeping with similar non-gravitational accelerations seen with comets within the solar system.

via Michele Bannister

Continue reading “Space Sunday: ‘Oumuamua, BFS and Tianhe-1”

Space Sunday: farewell and welcome back

One of the last images of Ceres returned by the Dawn mission which was officially declared ended on November 1st, 2018. Note the bright carbonate mineral deposits in Occator Crater to the right of the image. Credit: NASA/JPL

Two important space missions came to an end at the end of October 2018. The Kepler observatory, which spent nine years in deep space collecting data that detected thousands of planets orbiting stars outside our solar system; and the Dawn spacecraft, which spent 11 years orbiting and studying the main asteroid belt’s two largest objects, Vesta and Ceres.

Concerns had been growing for months over Kepler’s ability to continue working as a result of dwindling on-board propellant supplies, as the space observatory has had to use it thrusters a lot more than originally planned, following the failure of some of its pointing gyroscopes several years ago. Similarly, the end of the Dawn mission had been signed as a result of that vehicle also running low on orientation propellants.

Launched in 2007, Dawn was the first spacecraft to orbit a body between Mars and Jupiter, and the first to orbit more than one deep-space destination. From 2011 to 2012, the spacecraft studied the asteroid Vesta before pulling off an unprecedented manoeuvre by leaving orbit and travelling to the dwarf planet Ceres, which it observed for over 3.5 years. Even with the mission now officially over, Dawn will remain in a stable orbit around Ceres for decades, while among its many findings, Dawn helped scientists discover organics on Ceres and evidence that dwarf planets could have hosted oceans over a significant part of their history—and possibly still do.

Both missions were extended past their originally anticipated lifetime because of the innovative work of their engineers and scientists. In 2016, Dawn’s mission at Ceres was extended. In 2017, its mission at Ceres was extended again to study the dwarf planet from altitudes as low as 35 km (22 mi) above the surface, with the main goal of understanding the evolution of this dwarf planet.

Dawn depleted its hydrazine propellant on October 31st, 2018 while still actively engaged in studying Ceres. Without it, the vehicle could not keep its solar panels oriented towards the Sun in order to provide energy to its battery systems, resulting in a complete loss of contact with Earth. Attempts were made to re-establish communications through NASA’s Deep Space Network, but the loss of propellants had been expected, and the US space agency officially announced the mission as concluded on November 1st, 2018.

Ceres’ lonely mountain, Ahuna Mons, seen in a simulated perspective view with the elevation has been exaggerated by a factor of two. The view was made using enhanced-colour images from NASA’s Dawn mission. Credit: NASA/JPL

Among the more surprising discoveries Dawn made was the fact that small bodies in the solar system like Vesta and Ceres are more diverse in nature that had even been thought. Dawn also revealed that geological activity on Ceres had once been sufficient to raise a massive 5 km (3 mi) high cryovolcano, Ahuna Mons (or informally, The Lonely Mountain), and to create more than 300 bright features, called faculae. On Earth, these bright deposits of carbonate minerals are associated with water, suggesting Ceres may have, or had, a liquid water interior. The brightest of these deposits, in Occator Crater is also the largest deposit of carbonate minerals found beyond Earth.

Such is the amount of data returned by Dawn, analysing it all will still take several more years, as noted by the mission’s Principal Investigator, Carol Raymond:

In many ways, Dawn’s legacy is just beginning. Dawn’s data sets will be deeply mined by scientists working on how planets grow and differentiate, and when and where life could have formed in our solar system. Ceres and Vesta are important to the study of distant planetary systems, too, as they provide a glimpse of the conditions that may exist around young stars.

Kepler, meanwhile, was launched in 2009 and completed its primary mission in 2012, leading to the first mission extension. Then, in 2013, a second gyroscope failure left the observatory unable to continue in its primary operating mode. Instead, engineers found a way to use both solar pressure and the observatory’s manoeuvring jets to keep it pointing in a desired direction. This allowed a new mission, dubbed K2, to commence in 2014. It has been running ever since, gathering science from 19 different patches of sky with populations of stars, galaxies and solar system objects.

Kepler was officially retired on October 30th, 2018. For most of the year it had been showing signs of running out of propellants, and without them, it would be unable to maintain the correct orientation to either continue observations or turn itself to communicate with Earth.

As NASA’s first planet-hunting mission, Kepler has wildly exceeded all our expectations and paved the way for our exploration and search for life in the solar system and beyond. Not only did it show us how many planets could be out there, it sparked an entirely new and robust field of research that has taken the science community by storm. Its discoveries have shed a new light on our place in the universe, and illuminated the tantalizing mysteries and possibilities among the stars.

– NASA’s official announcement on Kepler’s retirement

Kepler by the numbers. Credit: NASA

Continue reading “Space Sunday: farewell and welcome back”