# Mission concepts for a tomography of an asteroid or other celestial body

Tomographies of various kinds are basically the only possibility right now to look deeper into asteroids or planets. On Earth, "signals" generated by earthquakes are for instance used for performing a tomography in a mathematical sense of the Earth and its core structure (seismic tomography in wikipedia, more details in a document of the Incorporated Research Institutions for Seismology).

In space, as far as I know, the only mission making use of a similar concept (for an asteroid) is Rosetta with its "COmet Nucleus Sounding Experiment by Radiowave Transmission" - please correct me if I am wrong.

There have been plenty of proposals for seismic networks on the Moon, etc. But are there any currently seriously investigated mission concepts with hopefully some actual funding, which contain at least one experiment/instrument of any sort that could perform a tomography of a celestial body?

EDIT: What I am kind of looking for are concepts, which result in a 3D representation of the interior of an object as you can find it in medical applications. Due to the fair number of seismometers and quakes here on Earth, you can actually search for anomalies within a plain shell model of the Earth. On the Moon, there were similar attempts during the Apollo era. Have a look at this paper: A. Khan, A. Pommier, G.A. Neumann, K. Mosegaard, 2013. The lunar moho and the internal structure of the Moon: A geophysical perspective. In: Tectonophysics. Figure 4 is interesting. Here, the limitation was the number of seismometers and useful seismic events. Besides, all seismometers were located on one hemisphere, thus further limiting the value of their data. The answer of @DeerHunter refers to InSight for Mars, which is based on the same concept and essentially has the same limitations.

• China's Chang'e 3 lunar rover that will be launched later this year will have radar equipment mounted on its underside that will allow it to image nearly one kilometer beneath the surface. – Gwen Jul 19 '13 at 4:14
• @Gwenn: Yep, I know. But compared to the Moon's radius of about 1,737 km, this is a bit pointless with respect to my question. – s-m-e Jul 22 '13 at 8:23
• InSight is the usual example. Underfunded, descoped... – Deer Hunter Jul 23 '13 at 21:40

The InSight mission fits your criteria. Quoting JPL:

• SEIS: To capture Mars' pulse, or its internal activity, InSight will carry a seismometer called SEIS to the surface of the Red Planet. SEIS will take precise measurements of quakes and other internal activity on Mars to better understand the planet's history and structure.

• HP3: To take Mars' temperature, a key indicator of planetary evolution, InSight will deploy a heat flow probe on the surface of Mars. The instrument, known as HP3, will hammer five meters into the Martian subsurface, deeper than all previous arms, scoops, drills and probes, to learn how much heat is coming from Mars' interior and reveal the planet's thermal history.

Why do I consider it tomography if there's only one sensor?

• It is possible to spot impact events with the help of Mars Reconnaissance Orbiter...
• ... and thus correlate seismic records with quantitative estimates of the force of impact and its precise areographic coordinates.

In words of Bruce Banerdt at the July 2013 meeting of MEPAG: (http://mepag.jpl.nasa.gov/meeting/jul-13/files/Banerdt%202013-0732%20MEPAG.pdf)

• Thanks for the answer, it is useful. You could say that this is a "quasi-tomography". There were similar experiments on the Moon during the Apollo flights. The mathematical limitation is, that you have to assume a model of spherical shells - point symmetry, in a way - for data analysis. However, this will not give you a kind of 3D-resolved representation of the Martian interior, which is a bit of what I am looking for. On a large scale, planets are point symmetric, but asteroids are certainly not ... – s-m-e Aug 12 '13 at 19:05
• @ernestopheles - alas, this will have to wait. There were plans to scatter sensors around the planet, but there's no funding for that. – Deer Hunter Aug 12 '13 at 19:10
• Yep ... you are right. That's why I was asking for concepts with 'actual funding' - whatever this could mean. Besides, I slightly edited my question. – s-m-e Aug 12 '13 at 19:26