Universiteit Leiden

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Melissa McClure

Tracing space ice and the building blocks of life

An unprecedented space telescope, an astrolab that makes space ice and molecules that may lead to the origin of life… The Ice Age project has all the prerequisites to become a very fascinating research project – if it is not one already. Leiden astronomers Melissa McClure, Harold Linnartz and Will Rocha will be some of the first scientists in the world to work with data from the recently launched James Webb space telescope. Their project Ice Age is 1 out of 13 selected Early Release Science programmes.

The building blocks of life

The molecules that make up the building blocks of life form well before planets themselves. They arise deep inside clouds of gas and dust. These clouds will eventually collapse and transform into planet-forming disks around young stars. In the coldness of space, dust grains inside these clouds become covered in a layer of ‘frost’. It’s on these icy grains, that increasingly complex molecules develop over time. The exact composition of the ice depends on the environmental conditions.

A kickstart of life on Earth?

‘With IceAge, we will study the evolution of icy grain in space across all physical stages of the star and planet formation process,’ says McClure, PI of the programme. ‘This way, we can find out how much of each ice species there is in the different ages and locations of molecular clouds. Which complex molecules survive the star formation process and make it to the planet-forming disk intact? Because those are the molecules that, embedded in comets, could end up on a planet to kickstart life as we know it. Scientists debate if this may have happened on Earth, and our observations can clarify whether this is physically possible.’

Creating snapshots from start to finish

For the Ice Age project, Webb will zoom in on a compact star-forming region in which the astronomers can observe ices in all different stages of star formation – from molecular cloud core to planet-forming disks where comets will eventually form. McClure: ‘This way, we can cover all stages in a small amount of observing time to create snapshots from start to finish.’

'A spectrum is like a unique fingerprint that tells us more about the composition of the ice'

Unique icy fingerprints

To do so, Webb will catch the infrared light emitted from the different locations and dissect it into its constituent wavelengths creating a so-called infrared spectrum. ‘Each ice species has a different molecular structure and therefore a characteristic spectrum,’ McClure explains. ‘It’s like a unique fingerprint that we can use to learn more about the composition of the ices at different locations and moments in time.’

This example spectrum illustrates the kinds of molecules that may be detected in star-forming regions, like the Eagle Nebula (background). Credits: NASA, ESA, the Hubble Heritage Team, M. McClure (Leiden University) and A. Boogert (University of Hawaii)

Why Webb is the one and only candidate

Webb is the perfect – and only – telescope for this mission because, first of all, high in space the incoming infrared signals are not blocked by the Earth’s atmosphere. Therefore, Web can look at a much wider range of wavelengths than ground-based telescopes. Furthermore, it’s also much more sensitive than any previous telescope in space, says McClure. ‘Add to that its higher spectral resolution and it’s unique ability to map a bigger area at once, and you understand why we're all so excited about Webb.’

How to make space ice?

But how do you know which fingerprint belongs to which ice species? That’s where co-PI Linnartz and Ice Age postdoc Rocha come in. In the Leiden Laboratory for Astrophysics, at extremely low pressures and temperatures just above absolute zero (~ -263°C), they create ices just like those in space.

IRASIS (InfraRed Absorption Setup for Ice Spectroscopy) is the instrument at the Laboratory for Astrophysics used to obtain spectra of space ices that will be compared with Webb's observations. Credits: LfA/Leiden Observatory

Linnartz: ‘Here, we are in full control of all parameters that influence the ice composition, such as temperature and porosity of the ice, and we can make various mixtures of water and other ice constituents. We then accurately measure the spectra of these ices, so we can compare them to the spectra Webb will soon provide us with.’

Software to prove the existence of lab build molecules

Rocha developed the special software to do so. ‘By putting the observations and lab spectra on top of each other, we can look for matches to prove the presence and abundance of specific molecules in space. And that, in turn, also tells us something about the environmental conditions in which they were formed.’

‘Since we depend on laboratory spectra with which to compare the observations, this laboratory data is essential,’ says Linnartz. ‘The more ices we can spectroscopically characterise, the less the observational results will be impaired by a lack of knowledge.’

Database with infrared ice spectra

Rocha’s software is freely available online at the Leiden Ice Database for Astrochemistry (LIDA). In the same database, Rocha and Linnartz also published a collection of no less than 1061 infrared ice spectra. Linnartz: ‘This database will be of great importance to all the different side projects of IceAge. It was also one of the reasons NASA picked our project as one out of 13 Early Release projects.’ McClure explains: ‘IceAge is a great project to kick-off with because it tests all of Webb’s observing instruments and will provide valuable exemplary data for the community to use.’

'Space Ice is such a hot topic!'

First Webb data expected in summer

On 24 January Webb is expected to reach its final orbital location. Then the researchers have to be patient for one last time for the system to get to its operational temperature and the instruments to be calibrated. Between June and July, the first data is expected. McClure: ‘We’re itching to get started and to get our first results. Linnartz: ‘Hopefully our results will inspire many projects to come. Space ice is such a hot topic!’

From workshop to leading science programme

Linnartz: ‘The initial idea for Ice Age originated during a workshop at the Lorentz Center in Leiden. We invited experts on space ice and instead of a paper, decided to work on a proposal for an Early Release Project. Out of over a 100 submissions worldwide, 13 were granted to work with Webb for the first time. It’s wonderful  that a workshop has led to a programme like ours.’

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