Space Sunday: a rover and some astronomy

After a treacherous journey, NASA’s Curiosity Mars rover has reached an area that is thought to have formed billions of years ago when the Red Planet’s water disappeared.

Lying part-way up the slopes of “Mount Sharp”, the mound of material deposited at the centre of Gale Crater (and formally called Aeolis Mons), is rich in salty minerals scientists think were left behind when the streams and ponds on the slopes of the mound finally dried up. As such, this region could hold tantalizing clues about how the Martian climate changed from being similar to Earth’s to the frozen, barren desert we know today.

These salty minerals were first spotted from orbit by NASA’s Mars Reconnaissance Orbiter before Curiosity arrived on Mars in 2012, and that discovery marked the deposits as a prime target for the rover to examine.  However, such is the rich diversity of rocks and minerals making up “Mount Sharp”, all of which have been subject to examination by the rover, it has taken the mission almost a decade to reach this “prime” target.

Even so, before Curiosity could obtain any samples from the site, the rover faced a couple of challenges.

The first lay in the fact that the rover’s position on “Mount Sharp” meant that the mission team had to drive and position the rover to ensure its antenna could remain aligned with the various orbiters it needs to use to communicate with Earth; this made navigating to the deposits a challenge, as has ensuring it can reach rocks that might yield interesting samples.

A view through “Paraitepuy Pass” captured by the MastCam on NASA’s Curiosity rover on August 14th, 2022, the 3,563rd Martian day, or sol, of the mission. Credits: NASA/JPL / MSSS

The second required further tests had to be carried out on the rover’s sample-gathering drill to ensure it would handle the stresses in cutting into the region’s rocks. As designed, the drill was intended to use a percussive action as it drilled into any target- but as I’ve reported in these pages, this hammering action started to affect the drilling mechanism as a whole, so a new algorithm was created and uploaded to the rover to minimise any use of the percussive action.

Because of this, the mission team now approach each sample gathering operation with an additional step: after scouring the surface of a sample rock to remove dust and debris, the team then position the drill bit against the rock and attempt to scratch the surface – any resultant marks would be a good indication the rock is soft enough to be drilled without the need for the hammer option.

In the case of this rock – nicknamed “Canaima” – no marks were left, indicating it might prove a difficult subject. However, a further test with the drill head turning revealed it could cut the rock without the use of the hammer action, so on October 3rd, 2022, Curiosity successfully obtained its 36th sample for on-board analysis.

A MastCam view of the 36th successful sample hole Curiosity has drilled, this one on the sulphate-rich rock dubbed “Canaima.” Inset: the hole as imaged by the Mars Hand Lens Imager (MAHlI) mounted on rover’s robot arm, along with the drill mechanism. These mages were taken on October 3rd, 2022, the mission’s 3,612th Martian day, or sol. Credits: NASA/JPL / MSSS

The route to this sulphate-rich area also required Curiosity pass through a narrow, sand-rich location dubbed “Paraitepuy Pass”, bordered on either side by slopes the rover could not drive over or along. Such is the nature of the sand the rover took over a month to traverse the pass, moving cautiously in order to avoid getting bogged-down. This meant that the rover celebrated its 10th anniversary crossing the pass.

The challenges also haven’t ended; the salty region comprises rocky terrain that is so uneven, it will be difficult for Curiosity to place all six wheels on stable ground. This isn’t a problem when on the move, but it could limit science operations in the area: if all of the rovers wheels are not in firm contact with the ground under them, operators won’t risk unfolding its instruments-loaded robot arm in case it clashes with jagged rocks.

Even so, the rover still has a lot of opportunities for science and discovery as it continues to climb “Mount Sharp”.

JWST Wows, HST, Chandra and IXPE Respond

It is now 100 days since the James Webb Space Telescope commenced operations, and in their most recent updates, NASA released a stunning image the observatory captured of the iconic Pillars of Creation.

The Pillars of Creation as imaged by the James Webb Space Telescope. Credit: NASA / ESA

Located in the Serpens constellation, roughly 6,500-7,000 light-years from Earth, the Pillars are gigantic “elephant trunks” of interstellar gas and dust, a birthplace of new stars,  constantly, if slowly being changed by the very stars born within them. They were imaged by the Hubble Space Telescope (HST) in 1995, the image becoming famous the world-over despite HST imaging them again it 2014. However, the image developed by JWST’s Near Infra-red Camera (NIRCam) eclipses the Hubble image, revealing the pillars and their surroundings in incredible detail.

Newly formed stars lie outside of the column. Seen merely as a few bright red orbs with strong diffraction spikes radiating from them, they are reveal by JWST as in their truer colours – blues, yellows, whites, indicative of their spectral classes, a veritable sea of stars, These are the stars that are causing the pillars to change and collapse as a mix of their gravities and radiative energy influence their form.

The Pillars of Creation as images by the Hubble Space Telescope in visible light (1995 – left) and by the James Webb Space Telescope in the near infra-red (right – 2022). Credit: NASA / ESA

Also visible along the edge of the pillars are wavy forms, the ejections of gas and dust from stars that are still forming. The crimson glow seen within some of these wave-like forms is the result of energetic hydrogen molecules interacting with the supersonic outbursts of the still-forming stars. Within the cloudy forms of the pillar are red points of light – newly-formed stars that are just a few hundred thousand years old, the light just stars to break through the surrounding clouds of dust and material.

Around all of this is a translucent blue glow, a mix of dust and gas known as the interstellar medium, found in the densest part of our galaxy’s disk. It serves to block the view of the deeper universe, bringing the Pillars of Creation to the fore.

This new view of the Pillars will help researchers revamp their models of star formation by identifying far more precise counts of newly formed stars, along with the quantities of gas and dust in the region. Over time, they will begin to build a clearer understanding of how stars form and burst out of these dusty clouds over millions of years.

However, Hubble isn’t to be entirely outdone. A team using images from Hubble, together with those captured by the Chandra X-Ray Observatory and NASA’s most recent Earth-orbiting observatory, the  Imaging X-ray Polarimetry Explorer (IXPE) to offer a remarkable image of a stellar remnant called Cassiopeia A (“Cass A”), located 11,000 light-years away and measuring 29 light-years across.

About three hundred years ago, the light from this supernova reached Earth for the first time. Since then, astronomers have been fascinated by the beauty of its structure and the powerful shockwaves that emanate from its centre. Cass A was selected for study by IXPE because the shock waves generated from the supernova that created it are some of the fastest in the Milky Way.

These shockwaves are carriers for synchrotron radiation a unique radiation that exists across a range of wavelengths. It is created within the extreme conditions found around such supernova remnants, where magnetic fields grab charged particles like electrons and protons and accelerate them to speeds close to that of light. As the particles accelerate, so the radiation becomes polarised, effectively becoming encoded with information about the supernova.

While the particles themselves are unable to escape the supernova remnants, the synchrotron radiation can, and its broad spectrum means it can be recorded by observatories like Chandra and IXPE, providing astronomers within insights into the formation of the supernova and the star which gave rise to it.

Cassiopeia A as imaged by the Chandra X-ray observatory has been investigated in polarized X-rays. Credit: NASA/CXC/SAO; IXPE: NASA/MSFC

By combining the Chandra and Hubble images, scientists have produced an image revealing Cass A as a glittering sapphire in space, . The white and gold specks seen throughout this image are optical light observations from the Hubble Space Telescope. The neon blue is X-ray data from NASA’s Chandra X-ray observatory, and the the fainter turquoise the observations from IXPE.

The composite image has allowed scientists to effectively “reverse engineer” the processes that are occurring within Cass A at small scales. These in turn have allowed them to discover that the magnetic fields fond within supernova remnants like Cass A are far more complex than had been previously been believed.

Chandra Also Works with JWST to Reveal the Beauty of the Universe

Images and data from the Chandra X-Ray observatory have also been combined with those from the James Webb Space Telescope to help offer new insights into the universe around us.

Chandra and JWST are particularly well-paired as they effectively operate at opposite ends of the energy spectrum: JWST is focused on observing in the infra-red, gathering data on the heat emitted by the objects it observes – infra-red wavelengths being very good at passing through the gas and dust of the interstellar medium without being absorbed or overly scattered, allowing astronomers to “see” deep into formations like the Pillars of Creation and others and discover the processes at work within them.

X-rays, meanwhile are produced by some of the most energetic events in the cosmos, like supernovae and pulsars. The radiation we get in the X-ray tells us about how these high energy processes operate. By combining data from both of these wavelengths, astronomers can build up  a clearer picture of the inner workings of some of the most complex astrophysical phenomena in the universe.

Stephan’s Quintet as seen in a composite image combining the infra-red of JWST with the X-Ray view of the Chandra X-Ray Observatory, revealing the interaction between two of the galaxies in the group and a shockwave passing through it. Credit: NASA / ESA

In this case, scientists have combined images of the galaxies within Stephan’s Quintet (one of the first subjects imaged by JWST at the start of its first science campaign) to map details of the interactions between the quartet of close-knit galaxies within the group (the fifth is purely the result of a line-of-sight alignment). While the JWST image reveals the galaxies in detail, on it own, it doesn’t clearly reveal a shockwave between two of them. Similarly, while Chandra is able to view the shockwave, it doesn’t see all the detail of the galaxies, But when combined, the two reveal not only the galaxies and the shockwave, they reveal the interactions between them, helping astronomers better understand the interplay of forces within the group.

Another image released by the team combines images from both Chandra and JWST of the Cartwheel Galaxy (ESO 350-40), located some 500 million light-years from Earth. It is regarded as one of the most complicated objects in the known cosmos. It is a part of a group of galaxies know as the Cartwheel Group; but whereas the others are regular spiral galaxies, the Cartwheel has a very complex, distinct form which astronomers are still trying to explain.

This is not the first time images of the Cartwheel Galaxy captured in different wavelengths have been composited into a single picture – in 2006, images from Chandra, Hubble, the Spitzer Observatory and the Galaxy Evolution Explorer. However, this image is more informative in terms of mapping the additional complexities of the magnetic and energy fields operating across the 144,300 light-year diameter galaxy.

A JWST / Chandra composite image of the Cartwheel Galaxy (large, right), which astronomers hope will reveal more of this complex structure’s mysteries. Credit: NASA / ESA

The team working on the images are still diving into all that these composites might reveal and have yet to formally publish their  findings / thinking. In the meantime these images on their own reveal just what an incredible and beautiful place our universe is.

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