## 2 Materials and Methods
### Aggregate Ability of the Regolith  
On the Moon, there are two morphological landforms, including highland regions and the flat Maria. The highland and mare terrains form nearly 83% and 17% of the Moon's surface, respectively. The mare regions are black in colour and basaltic in composition [54; 55]. On the other side, the highland regions comprise the felspathic formations described as anorthosite, which is again an igneous rock. Similarly to the Moon, Martian soils/rocks have basaltic genes interestingly. Due to the never-ending bombardment of lunar and Martian surfaces by small and large meteoroids, upper rocks have been extensively smashed into a silt-size powdered soil called regolith. The utilization of in situ resources (ISRUs) has acquired considerable attention amongst the space community. The on-site production of water, oxygen, hydrogen, helium 3, titanium, sulfur, and other precious elements from the lunar and Martian surfaces can be carried out via the direct processing of in situ regolith. Such invaluable elements will benefit human presence on the Moon and Mars's surfaces. This is a revolutionary breakthrough promoting the utilization of local aggregates instead of transported terrestrial materials. There are some industrial techniques by which new substances can be created from the in situ regolith (or igneous (basaltic) rocks) present on Mars and Moon. In this section, the potential applications of these on-site resources are discussed from the outpost's development perspective. The lunar and Martian regolith can be deployed for outpost development in two possible forms: raw and synthesized. In the raw form, regolith is utilized in the construction process while its natural composition and intact shape remain unchanged. For instance, raw regolith can be stored in some special bags, and then, they are accumulated on all sides of the outpost [56]. On the Moon, the collision of small-size particles with the lunar surface ceaselessly occurs since no atmosphere and magnetic field exist [57]. The regolith bagsserve as a shielding layer, protecting the outpost from particles, solar radiation, intensive temperature fluctuations, and possible meteoroid impacts. Another identical application of raw regolith is to directly deposit regolith on the structure and then covering such a regolith with membranes that are anchored to the ground [13; 14; 58; 59; 60]. The direction of the anchor is a key parameter in the stability of the structure [61]. The second more important application of the in situ regolith is using it in a synthesized form. In this case, the indigenous regolith is combined with other substances to constitute new, altered materials with far more compressive strength. To carry this out, the first simple way is blending an amount of regolith with additives or binders to create new mortars. The additives can be directly taken from the Earth to space, or alternatively, they may be produced via advanced techniques at the construction site. As an illustration, NASA has already assessed the combination of epoxy ICI Fiberite 934 binder with the Martian regolith to curtail surface radiation [62]. Via a combination of additives with the in situ regolith, the new materials will have further structural strength and can be molded into diverse shapes, such as bricks, blocks, voussoir, etc. This is the basis of the 3D-printed modules utilized in 3D printing technology applied for outpost construction [63]. In the 3D printing technique, the regolith is firstly sintered, and then, a special binder is added to the regolith to make a substance with lower porosity and higher strength. For sintering the regolith, a number of methods are applicable: laser sintering, solar sintering, and microwave sintering [64]. Regarding laser and solar sintering, it can be said that the complexity, high energy consumption, and environmental challenges restrict the large-scale usability of such methods [65; 66; 22; 67].