# Mars Book vs Solar System&Celestial Objects

The clearest difference is ads: Mars Book at none against Solar System&Celestial Objects's shown. Mars Book also leads on iOS requirement (9.0 vs 12.0). Solar System&Celestial Objects's advantage is update cadence (every 6 weeks vs every 13 months). On price, in-app purchases and device support there is nothing between them.

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

Mars Book ships an update every 13 months, Solar System&Celestial Objects every 6 weeks. The most recent releases landed on September 10, 2026 and May 16, 2026 respectively.

## The numbers

| Metric | Mars Book | Solar System&Celestial Objects |
| --- | --- | --- |
| Price | Free | Free |
| In-app purchases | No | No |
| Ads | **No** | Yes |
| Update frequency | Every 13 months | **Every 6 weeks** |
| Size | 14 MB | 62 MB |
| Requires iOS | **9.0** | 12.0 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Vixen Co.,Ltd.](https://appshunter.io/developer/536188843) | [NIKI TECH](https://appshunter.io/developer/1788609104) |

## What reviewers say

### Mars Book

[App page](https://appshunter.io/ios/app/mars-book/id1342509724)

**In-app purchases:** none


### Solar System&Celestial Objects

[App page](https://appshunter.io/ios/app/solar-system-and-celestial-objects/id6503188651)

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is Mars Book free?

Mars Book is free to download, with no in-app purchases.

### Is Solar System&Celestial Objects free?

Solar System&Celestial Objects is free to download, with no in-app purchases.

### Do Mars Book or Solar System&Celestial Objects have ads?

Solar System&Celestial Objects shows ads; Mars Book does not.

### Which is updated more often, Mars Book or Solar System&Celestial Objects?

Mars Book ships an update every 13 months, and Solar System&Celestial Objects every 6 weeks. Most recently, Mars Book was updated on September 10, 2026 and Solar System&Celestial Objects on May 16, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*