ESA EChO Exo-Gas Mission

[Selfsim]

Ok, so the Exoplanet Characterisation Observatory (EChO) project is one of four, (out of 47), major ESA Missions shortlisted in Feb 2011, for further assessment and study (in their Medium Class Cosmic Vision program) ...

EChO would be the first dedicated mission to investigate exoplanetary atmospheres, addressing the suitability of those planets for life and placing our Solar System in context.

It comes down to a sub 1 metre class telescope operating in the visible - thermal infrared (9.4 to 11 micron) range, to be placed in a quasi halo orbit around the second Sun-Earth Lagrange point (L2) - 1.5 million km from Earth..

The Cosmic Vison programme defines the high-level scientific questions which these candidate projects should be aimed at making progress towards:

Themes:
What are the conditions for planet formation and the emergence of life ?

A question that fascinates mankind is what was the succession of events after the Big Bang and the formation of stars and galaxies, and under which conditions, that led to the origin of life on Earth? Equally captivating is the question of whether life exists elsewhere in the Universe and, if so, in what forms, on which kind of planets and linked to which type of stars.

The flow-on primary mission goal is:

To characterise the atmospheres of nearby transiting exoplanets, including temperate super Earths ...
EChO will measure atmospheric transmission, reflection and emission spectra over a continuous wavelength range that spans the optical to thermal infrared. Through the detailed measurement of the spectral energy distribution and spectral emission from molecules such as water (H₂O), carbon monoxide (CO), carbon dioxide (CO₂), methane (CH₄) and ammonia (NH₃) it will be possible to establish many critical atmospheric parameters, including chemical composition and abundances, energy budgets, thermal structure and potentially temporal and spatial variation of atmospheric structure.

Ok, so in other words, exo-gas 'biomarkers'.

So, putting aside the planetary formation research goals (which as far as I'm concerned, aren't an issue), the only way I can see how this project can lead towards providing hard data in answer to the ESA Cosmic Vision ‘Life emergence’ component theme question (see above), is for there to be simultaneously, local planetary exploration aimed at discovering another instance of life in our Solar System.
And, lo and behold, item 1.3 Life and habitability in the Solar System covers it:

Goal
Explore in situ the surface and subsurface of solid bodies in the Solar System most likely to host – or have hosted – life

The JUICE mission which targets the localised exploration Jovian moons, in particular Ganymede, Europa and Callisto, was recently selected for the purpose (albeit a much larger mission, in a different category than EChO).

So, the noteworthy point is that the EChO mission requires the data from direct exploration missions, in order for the EChO data to be interpretable in the context of exo-life presence/absence). Without it, the EChO data can only support more speculative hypotheses.

If the exploration mission, (in this case, JUICE), doesn’t go ahead for some reason, then I don’t see how the EChO data can be constrained sufficiently to support any meaningful exo-life conclusions.

This seems to be exactly the situation NASA finds itself in at the moment !

Regards

[Paul Wally]

So, putting aside the planetary formation research goals (which as far as I'm concerned, aren't an issue),

Why is planetary formation not an issue for you?

If the exploration mission, (in this case, JUICE), doesn’t go ahead for some reason, then I don’t see how the EChO data can be constrained sufficiently to support any meaningful exo-life conclusions.

I don't think it's the data that must be constrained. It's the range of possible conclusions that must be constrained, but that can always happen if/when new discoveries are made in the future.

[Selfsim]

So, putting aside the planetary formation research goals (which as far as I'm concerned, aren't an issue),

Why is planetary formation not an issue for you?

By way of clarification, what I mean is that astronomical observational data contributes directly towards planetary formation theory. Such theory development is corroborated every time new instances are directly observed, thus resulting in a verified, incrementally progressive, evidence-based formation theory.

This is distinct from attempts at imagining a generalised exo-life theory from the same observations. Generalised exo-life so theorised, can only be inferred and not verified, over light-year distances. A second life instance is fundamentally a different phenomenon from an exo-planet instance.

I don't think it's the data that must be constrained. It's the range of possible conclusions that must be constrained, but that can always happen if/when new discoveries are made in the future.

Fair enough.
And the new discoveries to be made in the future, (applicable in this instance), would be facilitated by exploration of our local environment … these are necessary, in order for interpreting exo-gas data, gathered from light-year distant exo-atmospheres.

Regards

[Romanus]

I disagree for a couple of reasons:

1.) JUICE and EChO will be investigating two different kinds of bodies; Jovian moon analogues are not what we're looking for as promising extrasolar environments. A "super-Europa" around another star will--with the quality of data available in only the near-future--look like a featureless ice-ball. Ditto for a Titan analogue; we'll see a very cold body with a methane signature (IIRC, diatomic nitrogen is difficult to detect spectroscopically). It's kind of like saying that we need to study the Moon more fully to interpret other satellites in the Solar System; this is fine for old, unaltered bodies, but not so much for Io, Europa, Titan, Enceladus, etc.

2.) For the gaseous signatures / biomarkers EChO's looking for--a massive, temperate body with a substantial atmosphere--we have only Earth as an example. This does constrain the results, but like the concept of the habitable zone itself, it's a constraint that seems to work.

[MaDeR]

to be simultaneously, local planetary exploration aimed at discovering another instance of life in our Solar System.

Why do you require that? AFAIK there are no Second Earth in our solar system. Other proposed possible environments for life in our sytem are different form Earth in significant ways (some of them extremely, like Titan). They will be helpful, of course, but I ask you under context of this discussion - your cursade against remote detection of possibly habitable exo-planets.

[ravens_cry]

I think it's a great idea, and I am very happy we are doing this.
While there could conceivably be a method for creating oxygen atmospheres without life, and life on Earth that doesn't use and even hates oxygen shows that we are likely to miss some life, if we find an oxygen rich atmosphere it is a place to start looking further.
I wish these scientists and engineers all possible success.

[Selfsim]

Why do you require that? AFAIK there are no Second Earth in our solar system. Other proposed possible environments for life in our sytem are different form Earth in significant ways (some of them extremely, like Titan). They will be helpful, of course, but I ask you under context of this discussion - your cursade against remote detection of possibly habitable exo-planets.

Repeating the relevant part of ESA's strategy:

1.3 Life and habitability in the Solar System
Goal:
Explore in situ the surface and subsurface of solid bodies in the Solar System most likely to host – or have hosted – life.
...
The JUICE mission which targets the localised exploration Jovian moons, in particular Ganymede, Europa and Callisto, was recently selected for the purpose

Any findings flowing from this part of the overall strategy contribute towards the database needed to interpret remote exo-gas measurements.

At the moment, the only firmly established (verified) causal relationship between the 'bio-gases' we know of, and life, comes from Earth, which has only one type of life, generating significant metabolic gases. If the same exo-gases are detected remotely, (over light-year distances), we still won't know whether they were generated by Earth-like life metabolism, or some other presently unknown natural exo-processes.

Similarly, there is no reason to suspect whether or not other remotely detectable exo-gases are associated with some, as yet unknown, exo-biology, (or not). If an exo-life discovery is made within our Solar System, we will have evidence which relates exo-life to some type of confirmed, measurable bio-sign (maybe metabolic gases). More importantly, we will also be able to update assumptions about our universal life models, which will facilitate predictions from them. Even if local discoveries aren't found, we may be able to incrementally update our knowledge about where, and why, life wasn't found in that local 'Habitable Zone'. If only remote exo-gas detection projects proceed, then verification or null findings about exo-life, will not occur, and we'll be stuck with more conjectures, no valid basis for predictions and an Earth-centric model.

Honestly, I don't know how many times I've said this. I find it unfortunate that the concept seems so difficult to grasp. I'm quite clear about it though.

This is not about speculation: 'possibilities', 'plausibilities', or any other hypothetical ideas.

This is coming from the perspective that the scientific purpose of the search for exo-life is as an experimental test for a universal theory of life. It is a test !

This is about empirical experimental science ... it is not about development of another unconstrained, inferred, speculative hypothesis !

The NASA strategy is now effectively devoid of local exploration. The ESA strategy isn't. The curtailment of the NASA local exploration missions effectively kills off any chance for empirical scientific progress, specifically in the search for exo-life.

If it comes down to furthering knowledge about exo-life, exo-gas detection over light year distances, in isolation, simply cannot achieve this. It requires the data from local exploration. When it comes to priorities, local exploration is the local logical choice. One has to walk before one can run !

[MaDeR]

At the moment, the only firmly established (verified) causal relationship between the 'bio-gases' we know of, and life, comes from Earth, which has only one type of life, generating significant metabolic gases. If the same exo-gases are detected remotely, (over light-year distances), we still won't know whether they were generated by Earth-like life metabolism, or some other presently unknown natural exo-processes. (...) If an exo-life discovery is made within our Solar System, we will have evidence which relates exo-life to some type of confirmed, measurable bio-sign (maybe metabolic gases).

And why this other local exo-life discovery would be better than already known Earth life? We have "some type of confirmed, measurable bio-sign (maybe metabolic gases)" for Earth.

After all, you can make same argument for local exo-life (say, for example, Mars) discovery: we still won't know whether they (remotely detected exo-gases same as on Mars) were generated by Mars-like life metabolism.

[Selfsim]

And why this other local exo-life discovery would be better than already known Earth life? We have "some type of confirmed, measurable bio-sign (maybe metabolic gases)" for Earth.

I never said it would be 'better' than anything else !
It would however, be the first non-Earth based lifeform for which we could directly confirm an exo-gas causality relationship, as a direct consequence of local biological testing (provided it exhibits metabolism) ! We cannot do this over light-year distances because we can't get to the exo-biological sample in order to apply the appropriate tests !

Having two instances may allow for, at least, the establishment of a trajectory for extrapolation and prediction, within the scope of developing a universal theory of life !