The Vedas are eternal, i am not sure which part of the vedas mentions this, but it widely acknowledged that unless and until one performs certain purification karma's which are required to attain a certain planet he cannot reach there.
The species on a particular planet are made of the elements benevolent to it.
Vedas mention that one need to have certain qualifications to attain higher planets.
So the people who had gone to moon must have attained the qualification in their previous lives(provided the people landing on moon is true).
The planets mentioned as navagrahas or other higher or lower planets/lokas are to be known fully what the sages had mentioned in the vedas. Whether they are in physical plane/ spiritual plane. We need to understand what the sages actually meant of different lokas before considering the validity of the vedas.
No one of the present can perfectly say about the different lokas given in various scriptures, they can be best known from compiler himself the sage Bhagavan Veda-Vyasa who is believed to be a chiranjeevi. Their are no concrete evidences of people contacting veda-vyas.
How the sages might have known about different lokas thousands of years ago and how could they describe them ?
How did they prescribe the qualifications required ?
All the conception of lokas/planets are nowadays run on the belief/faith system as the ability to tap that knowledge is lost from the present generation.
So one should be able to meditate and vibrate your brain to a particular frequency to get the knowledge you required from this infinite realm.
"The description about different lokas is given in the atharveda, Srimad bhagavatam canto 2 chapter 5 from sloka number 38, in vishnu purana chapter 7 etc."
As per SB Each and every loka has some specific attributes ie. the people who attained the requirements/qualifications will attain it.
Out of the 14 mentioned lokas in above mentioned scriptures, the 7 heavenly planets and their attributes are
1 Satya-loka: Brahma's loka. Satya-loka planetary system is not eternal. Abode of Truth or of Brahma, where atman are released from the necessity of rebirth.
2 Tapa-loka: Abode of tapas or of other deities. Ayohnija devadas live here.
3 Jana-loka: Abode of the sons of God Brahma.
4 Mahar-loka: The abode of great sages and enlightened beings like Markendeya and other rishies.
5 Svar-loka: Region between the sun and polar star, the heaven of the god Indra. Indra, devatas, Rishies, Gandharvas and Apsaras live here: a heavenly paradise of pleasure, where all the 330 million Hindu gods (Deva) reside along with the king of gods, Indra.
6 Bhuvar-loka (aka Pitri Loka): Sun, planets, stars. Space between earth and the sun, inhabited by semi-divine beings. The a real region, the atmosphere, the life-force.
7 Bhur-loka: Man and animals live here. The Vishnu Purana says that the earth is merely one
of thousands of billions of inhabited worlds like itself to be found in the universe.
Different realms of Patala are ruled by different demons and Nagas; usually with the Nagas headed by Vasuki assigned to the lowest realm.Vayu Purana records each realm of Patala has cities in it.
The 7 hellish planets are
8 Atala-loka: Atala is ruled by Bala - a son of Maya - who possesses mystical powers. By one yawn, Bala created three types of women - svairiṇīs ("self-willed"), who like to marry men from their own group; kāmiṇīs ("lustful"), who marry men from any group, and the puḿścalīs ("whorish"), who keep changing their partners. When a man enters Atala, these women enchant him and serve him an intoxicating cannabis drink that induces sexual energy in the man. Then, these women enjoy sexual play with the traveller, who feels to be stronger than ten thousand elephants and forgets impending death.
9 Vitala-loka: Vitala is ruled by the god Hara-Bhava - a form of Shiva, who dwells with attendant ganas including ghosts and goblins as the master of gold mines. The residents of this realm are adorned with gold from this region.
10 Sutala-loka: Sutala is the kingdom of the pious demon king Bali.
11 Talatala-loka: Talātala is the realm of the demon-architect Maya, who is well-versed in sorcery. Shiva, as Tripurantaka, destroyed the three cities of Maya but was later pleased with Maya and gave him this realm and promised to protect him.
12 Mahatala-loka: Mahātala is the abode of many-hooded Nagas (serpents) - the sons of Kadru, headed by the Krodhavasha (Irascible) band of Kuhaka, Taksshaka, Kaliya and Sushena. They live here with their families in peace but always fear Garuda, the eagle-man.
13 Rasatala-loka: Rasātala is the home of the demons - Danavas and Daityas, who are mighty but cruel. They are the eternal foes of Devas (the gods). They live in holes like serpents.
14 Patala-loka: The lowest realm is called Patala or Nagaloka, the region of the Nagas, ruled by Vasuki. Here live several Nagas with many hoods. Each of their hood is decorated by a jewel, whose light illuminates this realm.
Many contemporary explanations are given for these lokas so as to how to understand them and yet it is difficult to comprehend for us as no concrete conclusion has come out.